•Ca5MgSi3O12 ceramics were developed as a new biomaterial.•Ca5MgSi3O12 shows an in vitro bioactivity by inducing bone-like HA.•The ceramic has good mechanical properties as potential bone material.•The cell culture experiments are conducted confirming the reliability of the ceramics as a potential candidate.In this work, the new calcium-magnesium-silicate Ca5MgSi3O12 ceramic was made via traditional solid-state reaction. The bioactivities were investigated by immerging the as-made ceramics in simulated body fluid (SBF) for different time at body temperature (37 °C). Then the samples were taken to measure X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy-dispersive spectra (EDS), and Fourier transform infrared spectroscopy (FT-IR) measurements. The bone-like hydroxyapatite nanoparticles formation was observed on the ceramic surfaces after the immersion in SBF solutions. Ca5MgSi3O12 ceramics possess the Young’s modulus and the bending strength and of 96.3 ± 1.2 GPa and 98.7 ± 2.3 MPa, respectively. The data suggest that Ca5MgSi3O12 ceramics can quickly induce HA new layers after soaking in SBF. Ca5MgSi3O12 ceramics are potential to be used as biomaterials for bone-tissue repair. The cell adherence and proliferation experiments are conducted confirming the reliability of the ceramics as a potential candidate.Download high-res image (224KB)Download full-size image

•A new semiconductor nanoparticle AgNb7O18 was prepared.•The silver niobate has a typical perovskite-like structure.•AgNb7O18 shows an efficient absorption with a narrow gap 2.76 eV.•AgNb7O18 has an efficient photocatalytic activity on MB photo-degradation.•The photocatalysis mechanism and stabilities were discussed.Silver-containing niobate AgNb7O18 nanoparticles were prepared via sol-gel polymerized complex synthesis. The sample was given a good XRD Rietveld refinement in a typical perovskite-like structure. The detailed surface properties of AgNb7O18 nanoparticles were tested by SEM, EDS, TEM, nitrogen adsorption-desorption isotherms and XPS measurements. AgNb7O18 is characterized via a direct transition and the band energy is 2.76 eV. The hybridization between O 2p and Ag 3d states in valence band contributes to the narrowed band gap. The first principles electronic structure elucidation supports the narrow band gap of AgNb7O18. The sample shows an efficient degradation of methylene blue dye (MB) solutions. The trapping tests were performed to elucidate the real active species in the photocatalytic reactions. The results indicate that the superoxide radical is the main active species in the photocatalytic system, and the photocatalyst also shows a good stability and durability.

•A new silver-containing niobate nanoparticle AgNb13O33 was prepared.•Typical perovskite-like structure was verified by Rietveld refinements.•AgNb7O18 shows an efficient absorption with a narrow gap 2.81 eV.•AgNb7O18 has an efficient photocatalytic activity on MB photo-degradation.•AgNb13O33 has more advanced photocatalytic activities than Nb2O5.Ag-containing niobate AgNb13O33 has been prepared by the sol–gel polymerized complex method. The structure was investigated via a good XRD Rietveld refinement in a typical perovskite-like framework. The morphological properties of the AgNb13O33 nanoparticles were tested via transmission electron microscopy (TEM), scanning electron microscope (SEM), and energy dispersive spectra (EDS) measurements. AgNb13O33 is a typical direct allowed semiconductor with band energy of 2.81 eV, which is much narrower than 3.4 eV of Nb2O5. This silver niobate can harvest both UV and near UV light, which is benefited from the (O-2p/Ag-4d) hybridization in the valence band. The photocatalytic abilities of AgNb13O33 nanoparticles were reported. The sample presents more efficient photocatalytic effects on photo-degradation of methylene blue (MB) dye solutions than that of Nb2O5. The photocatalytic mechanism was discussed on band energy levels, trapping experiments, photoluminescence and the decay lifetime.Download high-res image (228KB)Download full-size image

•A new titanate semiconductor NaFeTi3O8 was prepared.•Rietveld refinement was given in isostructural structure with titanium dioxide bronze.•Special 2D layered structure vertically ran through 1D channels.•Optical absorption and the indirect allowed band transitions were reported.•Multivalent characteristics of Fe and Ti were confirmed by calculations and experiments.A new ferrotitanate semiconductor NaFeTi3O8 was developed by sol−gel citrate complexation synthesis. The sample preferentially developed into nanorods. The nanorods showed good XRD Rietveld refinements in the isostructure with Na0.2TiO2. The structure retains the two-dimensional layers of (Fe/Ti)O6 octahedra and one-dimension channels in the structure. SEM, TEM, EDS, and specific surface area analysis were employed to characterize the samples. Results showed that the optical absorption of NaFeTi3O8 nanorods is in the visible wavelength region. The direct allowed bandgap (2.12 eV) shows the characteristic charge-transfer transitions of O 2p/Fe 3d→(Ti/Fe) 3d. The d–d allowed transitions in the FeO6 octahedron presented considerable contributions to the narrow bandgap. NaFeTi3O8 exhibited potential as a photocatalyst for RhB photodegradation under visible light excitation (λ > 420 nm). Photocatalytic activities are discussed in relation to the structural properties.Download high-res image (146KB)Download full-size image

•YK3B6O12:RE3+ (RE = Eu, Ce, Tb) phosphors were developed to near-UV white LED.•Under near UV light excitation, the phosphors exhibit the characteristic tricolor emission.•The application performances for the phosphors were reported for the first time.Polycrystalline phosphors YK3B6O12:RE3+ (RE = Eu, Ce, Tb) were prepared by the solid-state synthesis. The single crystal-phases of the samples were confirmed by X-ray powder diffraction (XRD) measurements and the structural refinements. The field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and electron dispersive X-ray (EDX) measurements were applied to analyze the morphologies of the phosphors. The photoluminescence excitation spectra (PLE) and emission (PL) spectra, decay curves and lifetimes were investigated. Under the near-UV light excitation, YK3B6O12:Eu3+, YK3B6O12:Ce3+, and YK3B6O12:Tb3+ phosphors exhibit the characteristic emission transitions from Ce3+ (5d→4f transitions in blue color), Eu3+ (5D0→7F2, red color), and Tb3+ (5D4→7F5, green color), respectively. The luminescence internal quantum efficiency (QE), the optimal doping level and the thermal stability with the activation energy (ΔE) were measured. The result in this work could be useful for the further applications of this new host as a potential phosphor.

•New ilmenite-type semiconductor Ni3TeO6 was prepared.•The sample developed in typical nanorodsith a diameter of 10–15 nm.•The optical properties and band structure were firstly reported.•Photochemistry experiments confirmed its degradation on dye pollution.Ni3TeO6 semiconductor was synthesized by the sol-gel route. The crystalline phase was verified by XRD measurements together with Rietveld refinements. The surface morphologies were studied by TEM, SEM, EDX and XPS measurements. Ni3TeO6 semiconductor shows a high optical absorption for UV and visible light with a band gap of 2.48 eV characterized by the charge-transfer transitions of O2−→Ni-3d in UV and visible wavelength light. The photochemistry characteristic was investigated by the photocatalytic degradation of methylene blue (MB) dye solutions driven by visible-light. The nanoparticles were efficient in photo-degrading organic dye solutions. The photocatalysis activity and the mechanism were discussed on its structural properties.

•Mg3(BO3)F3:Eu2+ was developed by the solid-state reaction.•The emission shows dominated 4f7(6P7/2)→4f7(8S7/2) transitions.•Mg3(BO3)F3:Eu2+presents bright blue color with absolute QE of 83%.•It has an excellent thermal stability with activation energy 0.71eV.Eu2+-doped Mg3(BO3)F3 phosphors were synthesized by solid-state reaction. The structural refinement, the luminescence and decay curves were investigated. The phosphor presents a broad emission band assigned to 4f65d→4f7(8S7/2) transitions in blue range, which was overlapped with the peculiar 4f7(6P7/2)→4f7(8S7/2) transitions even at room temperature. In addition, the 4f7(6P7/2)→4f7(8S7/2) transition presents extremely strong intensity compared with the peculiar 4f7(6P7/2)→4f7(8S7/2) transitions. The decay properties and the thermal activation energy (ΔE) were reported. It shows high activation energy of 0.71 eV on temperature quenching. The maximum absolute quantum efficiency (QE) was measured to be 83% under UV light. The phosphor could deserve further investigations because of its peculiar spectral characteristics for basic studies and excellent application performances.

Ca2B2O5:RE (RE = Eu3+, Tb3+, Dy3+) nanofibers were synthesized by the hydrothermal reaction method. The structural refinement was conducted on the base of the X-ray powder diffraction (XRD) measurements. The surface properties of the Ca2B2O5:RE (RE = Eu3+, Tb3+, Dy3+) nanofibers were investigated by the measurements such as the scanning electron microscope (SEM), transmission electron microscope (TEM), and the energy dispersive spectrum (EDS). The nanofiber has a diameter of about 100 nm and a length of several micrometers. The luminescence properties such as photoluminescence excitation (PLE) and emission spectra (PL), decay lifetime, color coordinates, and the absolute internal quantum efficiency (QE) were reported. Ca2B2O5:Eu3+ nanofibers show the red luminescence with CIE coordinates of (x = 0.41, y = 0.51) and the luminescence lifetime of 0.63 ms. The luminescence of Ca2B2O5:Tb3+ nanofibers is green color (x = 0.29, y = 0.53) with the lifetime of 2.13 ms. However, Dy3+-doped Ca2B2O5 nanofibers present a single-phase white-color phosphor with the fluorescence decay of 3.05 ms. Upon near-UV excitation, the absolute quantum efficiency is measured to be 65, 35, and 37 % for Eu3+-, Tb3+-, Dy3+-doped Ca2B2O5 nanofibers, respectively. It is suggested that Ca2B2O5:RE (RE = Eu3+, Tb3+, Dy3+) nanofibers could be an efficient phosphor for lighting and display.

Calcium borosilicate Ca2SiB2O7 ceramics were prepared by the conventional solid-state reaction. The detailed crystal structure of the as-prepared ceramics was investigated by X-ray diffraction and structural refinements studies. The mechanical properties were measured by the bending strength and elastic modulus. In vitro hydroxyapatite mineralization ability was investigated by soaking the ceramics in simulated body fluid (SBF) at temperature 37 °C for various time periods. HA needles can be easily in vitro induced when the ceramics were soaked in SBF solutions. Scanning electron microscopy (SEM), X-ray diffraction patterns and Fourier transform infrared spectroscopy (FT-IR) analysis were applied to investigate the samples before and after immersion in SBF solutions. The elemental compositions of a hydroxyapatite layer on the surface of ceramics during mineralization were confirmed by X-ray energy-dispersive spectra (EDS). The in vitro mineralization ability was discussed on the base of the structural characteristics of Ca2SiB2O7 ceramic such as the silanol (Si–OH), B–OH groups and pentagonal tunnels and layered structure. The results confirmed that Ca2SiB2O7 ceramics possess good bioactivity and mechanical properties.

A Ni2+-containing vanadate, K2Ni(VO3)4 was developed as a new visible-light-driven photocatalyst. The nanoparticles were prepared by the modified Pechini method. The sample was characterized by the measurements such as X-ray powder diffraction, scanning electron microscope, and UV–Vis absorption spectrum. The photocatalytic activity of K2Ni(VO3)4 nanoparticles was evaluated by the photodegradation of methylene blue under visible-light irradiation in air. K2Ni(VO3)4 shows a photocatalytic activity due to the efficient absorption in the UV–Visible-light wavelength region with a narrowed band-gap energy of 2.08 eV and an indirectly allowed electronic transition. These results indicate that this vanadate garnet could be a potential photocatalyst driven by visible light. The effective photocatalytic activity was discussed on the basis of the special structural characteristic such as heavily distorted NiO6, rich, activated optical centers with tunnel structure for high photocatalytic capacity, and discussed on the basis of the photoluminescence and the decay lifetime.

The red-emitting Eu3+-doped rare earth antimonates R3SbO7 (R = La, Gd, Y) were prepared by high-temperature solid-state reaction. The crystal-phase formations were verified by X-ray powder diffraction (XRD) and structural refinements. The luminescence properties such as photoluminescence (PL) excitation and emission spectra, fluorescence decay curves, absolute luminescence quantum efficiency (QE), CIE color coordinates and the dependence of luminescence intensity on doping level were investigated. The luminescence QE, CIE color coordinates, and the spectrum characteristics of Eu3+ ions have a strong dependence on both R (La, Gd, Y) cations and Eu3+ doping levels. The 5D0 → 7F4 emission peak at 710 nm was the dominant transition in Eu3+-doped La3SbO7, while 5D0 → 7F0 at 580 nm was the strongest transition in Eu3+-doped Y3SbO7. The luminescence properties were discussed on the basis of the crystal structure. Different Eu3+ luminescence centers, such as isolated centers, pair broadening, and cluster centers, were discussed based on the dependence of the lifetime values on Eu3+ concentration. The luminescence QE of La3SbO7:0.4Eu3+ can reach 63.8% under excitation of UV light at room temperature; thus, it can have potential application as a red-emitting phosphor for solid-state lighting.

CaB2O4 powders and ceramics were prepared by the conventional solid-state reaction. In vitro hydroxyapatite (HA) mineralization was investigated by soaking the samples in simulated body fluid (SBF) for various time periods. X-ray diffraction and structural refinements, scanning electron microscopy and X-ray energy-dispersive spectra measurements were applied to investigate apatite formation before and after immersion in SBF. HA can easily form flower-like nanostructures with nano-needles even when soaked in SBF for several hours. The in vitro bioactivity of CaB2O4 was attributed to easy formation of B–OH groups in the CaB2O4 structure when soaked in SBF solutions. In the process of mineralization, the luminescence evolution of Eu3+ ions, a well-known structural probe, was detected by photoluminescence spectra and photoluminescence decay curves. This suggested that the process of mineralization can be monitored by the luminescence intensity of Eu3+ ions in the mineralization products. The current study will open up a new and simple in vivo avenue for in situ monitoring of hydroxyapatite conversion using a fiber luminescence spectrometer.

The concentration effect on the photoluminescence (PL) of the praseodymium Pr3+ ion is studied at 298–12 K for barium gadolinium molybdate (BaGd2(MoO4)4, called BGM) crystals with a wide Pr3+ concentration range of 0.05–25.0 mol%. Three types of concentration dependences are observed for the emissions although all types show PL quenching at high concentrations. The first type (Type A) has the maximum PL intensity at about 10 mol% with a non-zero intensity at high concentrations, which is observed for the 3P0 emissions except for emission at 621 nm. The second and third types (Type B-1 and B-2) have the maximum at about 1 mol% with a finite residual intensity and nearly zero intensity at high concentrations, respectively, which are observed for the 621 nm emission and all the 1D2 emissions. It is suggested that the energy migration mechanism is responsible for Type A, while the non-resonant cross-relaxation is responsible for Type B-1 and the resonant cross-relaxation for Type B-2.

A yellow-emitting nanophosphor of Ce3+-activated Sr3LuAl2O7.5 was prepared by chemical sol–gel method. The X-ray powder diffraction and scanning electron microscopy were applied to characterize the phosphors. The luminescence properties such as the photoluminescence (PL) excitation and emission spectra, the internal quantum efficiency (QE) and the luminescence decay curve (lifetime) were investigated. The Ce3+-activator concentration has an influence on the luminescence properties. Ce3+-activated Sr3LuAl2O7.5 exhibits brightest yellow emission with the internal quantum efficiency of 57%. The thermal stability of the yellow-emitting phosphor was evaluated by the temperature-dependent luminescence and the activation energy for thermal quenching. The luminescence properties of Ce3+-activated Sr3LuAl2O7.5 was discussed in comparisons with famous yellow-emitting YAG:Ce3+. This new nanophosphor could be a potential yellow-emitting phosphor for an application in lighting and display.

•We firstly developed a red-emitting silicon fluoride acrylate-Eu(III) copolymer.•SFA-Eu(III) copolymer can be excited by wavelength in near-UV and blue regions.•Eu3+ ions occupy several disordered crystallographic sites in the copolymer.•SFA-Eu(III) copolymer displays an ideal thermal stability and cold endurance.•SFA-Eu(III) copolymer could be a potential red material to be used for white LEDs.A red-emitting silicon fluoride acrylate (SFA)-Eu(III) copolymer was prepared based on water-in-oil emulsion polymerization method. Its photoluminescence including the temporal decay was studied in addition to the thermal properties. Of the emissions due to the 5D0 → 7FJ (J = 0–4) transitions of Eu3+ ions, an intense red emission due to 5D0 → 7F2 transition was observed at 618 nm under the 395 nm excitation, together with a weak 5D0 → 7F0 emission at 580 nm. Compared with some commercial phosphor, the SFA-Eu(III) copolymer also have a higher QE value. From the optical properties it was suggested that Eu3+ ions were located at the disordered non-inversion Eu3+ sites in the copolymer. The glass transition temperature (Tg) was estimated about −51.5 °C from a differential scanning calorimetric curve, while chemical decomposition was estimated to start from 385 °C from a thermogravimetry analysis curve. Taking into account the thermal stability in a wide temperature range from −51.5 °C to 385 °C, the SFA-Eu(III) copolymer is expected to act as a potential red component for near-UV excited white LEDs.

•A novel orange-emitting Ba4R2ZrWO12:Eu3+ (R=La, Gd, Y) has been synthesized by the solid-state reaction method.•The abnormally high intensity of 5D0→7F0 transition from Eu3+ ions was firstly observed in Eu3+-doped tungstate.•Ba4R2ZrWO12:Eu3+ (R=La, Gd, Y) presents high quantum efficiency and thermal stability.A novel orange-emitting tungstate of Eu3+-doped Ba4R2ZrWO12 (R=La, Gd, Y) was successfully synthesized. The samples were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The luminescence properties such as photoluminescence (PL) excitation and emission spectra, decay curves, CIE color coordinates and quantum efficiency (QE) were investigated. The thermal stability was discussed from the luminescence decay and lifetimes. The 5D0→7F0 transition of Eu3+ is abnormally stronger than the 5D0→7F1,2 transitions. The tungstate can be efficiently excited by UV and near-UV light and exhibits a bright orange luminescence. The luminescence mechanism was briefly discussed.

•BaGd2(MoO4)4:Yb3+ was first developed to be a near-infrared converter.•The polycrystal presents enhanced photosensitivity in the range of 260–375 nm.•BaGd2(MoO4)4:Yb3+ has an intense NIR emission around 1000 nm, which perfectly matches the maximum spectral response of Si-based solar cells.•BaGd2(MoO4)4:Yb3+ shows high quantum efficiency of 37%.Efficient conversion from ultraviolet (UV) light to near infrared (NIR) emission has been demonstrated in a series of BaGd2−xYbx(MoO4)4 (x=0.001−2.0, i.e., Yb3+ concentration=0.05–100 mol%) polycrystals. The samples presented enhanced photosensitivity below 375 nm. Under UV light, an intense NIR emission around 1000 nm from 2F5/2→2F7/2 transitions of Yb3+ was observed, which just corresponds to spectral response of Si solar cells. The emission intensity in NIR region showed a dependence on Yb3+ contents. Taking into account the photoluminescence quantum efficiency, the optimal doping to increase the conversion efficiency of Si-solar cells was suggested to be 20 mol%. Diffuse reflectance and luminescence spectra were also systematically investigated to propose a reasonable mechanism for energy conversion process from the photo-excited charge transfer states.

•A visible-light-driven photocatalyst was prepared by solid state reaction.•Photocatalytic ability of CaZnV2O7 is related to its special crystal structure.•Ni2+ doping can narrow the band-gap energy and enhance the photocatalytic effect.•CaZnV2O7 would have a potential application in environment protection.A new visible-light-driven photocatalyst of pyrovanadate CaZnV2O7 was synthesized by the conventional solid-state reaction method. The polycrystalline samples were investigated by the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and UV–vis diffuse absorption spectra measurements. CaZnV2O7 shows intense absorption bands in the visible light region due to band gap transitions. Ni2+-doping in CaZnV2O7 can narrow the band gap energy from 2.362 eV to 2.275 eV. Photocatalytic activities by photo-degradation reaction of methylene blue (MB) were investigated under visible-light irradiation. The results indicate that this pyrovanadate could be a potential photocatalyst driven by visible-light.

•A novel green pyrophosphate pigment BaCr2(P2O7)2 was firstly synthesized.•Cr3+ ion acts as a chromophore cation, enhancing the green color greatly.•A significantly high solar reflectance of 90% indicates its cooling function.•Durable chemical stability were found in BaCr2(P2O7)2 and ceramics.A novel pyrophosphate BaCr2(P2O7)2 was synthesized by the conventional solid-state reaction. The X-ray diffraction (XRD), FTIR spectrum, scanning electron microscopy (SEM) and ultraviolet–visible (UV–Vis) near infrared (NIR) reflectance spectra were applied to characterize the powders. The refractive indexes and nature of the VB and CB were determined. The structure, color properties and application were investigated. The results reveal that the anomalist bodies with smooth surfaces were obtained at 1200 °C with a mean size of 3 μm. A high reflectance peak at 535 nm was observed in the visible region, which is associated with the brilliant and deep green color of this pigment. With all the acids, alkali and deionized water treatment, the polycrystalline pigment BaCr2(P2O7)2 was found to be durable in chemical stability. The significantly high NIR solar reflectance of BaCr2(P2O7)2 is 90.0%, a higher cooling ability, so it has been selected to be tested as cool green pigment in ceramics. Moreover, this novel pyrophosphate pigment has great potential as cool pigment for surface coating applications.

Niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y) were prepared by conventional high-temperature solid-state reaction. The formation of a single-phase compound with triple-layered perovskite-type structure was verified through X-ray diffraction (XRD) studies. The luminescence characteristics such as photoluminescence excitation and emission spectra, X-ray-excited luminescence (XEL), Stokes shift, decay curves, and color coordinates were investigated. The niobates can be efficiently excited by UV light and present luminescence behaviors with rich luminescence colors. Under excitation by ultraviolet radiation, CaRNb3O10 (R = La, Gd, Yb, or Y) exhibits strong blue luminescence due to the self-activation center of the octahedral NbO6 groups, even at room temperature. For the materials of composition CaRNb3O10 (R = Sm, Eu, Dy, or Er), the excitation at the host band produces a characteristic luminescence of rare earth ions, indicating a host–guest energy transfer process. CaRNb3O10 (R = Eu) has the strongest luminescence intensity, which can be efficiently excitated by near UV wavelength. It could be suggested to be a potential candidate for the application on near-UV excited white LEDs.

Eu2+- and Eu3+-doped MgZn2(PO4)2 were prepared using the high temperature solid-state reaction method. The excitation spectra in the UV and VUV region, the emission spectra, and the luminescence decay curves of the Eu2+ and Eu3+ ions were investigated. The crystallographic distributions of the Eu2+ and Eu3+ sites in MgZn2(PO4)2 lattices are different. MgZn2(PO4)2:Eu2+ presents a bluish green luminescence with two distinct emission centers at 450 and 525 nm. MgZn2(PO4)2:Eu3+ presents an reddish orange color with luminescence transitions from the 5D0 level of the Eu3+ ions. There exist two Eu2+-crystallographic sites in MgZn2(PO4)2:Eu2+, which occupy both Mg2+ and Zn2+ sites. However, there is only one Eu3+-site in the MgZn2(PO4)2:Eu3+ lattices, which was confirmed by site-selective excitation and emission spectroscopy, and the luminescence decay in the 5D0 → 7F0 region of the Eu3+ ions under a pulsed, tunable, narrowband dye laser. The Eu3+ ion was suggested to occupy the octahedral Mg2+-site in the MgZn2(PO4)2 lattices. The spectral characteristics, the temperature-dependent luminescence intensity and activation energies of thermal stabilities and the microstructures were discussed on the basis of the crystal structure and the luminescence results.

A series of red emitting phosphors Sr9Eu2W4−xMoxO24 (x = 0–4) have been synthesized by solid-state reactions and their crystal structures, photoluminescence properties were studied. The excitation and emission spectra of Sr9Eu2W4−xMoxO24 phosphors can be modified by Mo6+ doping. As the molybdate content increased, the Eu3+ emission intensity of Sr9Eu2W4−xMoxO24 (x = 0–4) under 395 nm excitation was found to increase and reached a maximum at x = 2. The excitation spectra, the emission intensities and the chromaticity coordinates of Sr9Eu2W4−xMoxO24 (x = 2) were compared to those of the conventional red phosphor Y2O2S: Eu3+. The intense red-emission under near-UV excitation suggests that Sr9Eu2W4−xMoxO24 (x = 2) could be a potential candidate for white light generation by using near-UV LEDs. In this study, the effects of Mo6+ doping on the crystal structure and photoluminescence properties of Sr9Eu2W4−xMoxO24 were discussed.

Eu2+-activated K4CaSi3O9 phosphors were synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra were investigated. The phosphor presents bright yellowish-green-emitting luminescence under the excitation of UV and near UV light. The luminescence absolute quantum efficiencies of the phosphors with different Eu2+-doping levels (1.0–5.0 mol%) were measured. The crystal structure and the site-occupancy of Eu2+ ions doped in K4CaSi3O9 crystal lattice were discussed. Two different Eu2+ centers were assigned according to the crystal structure and the luminescence characteristics. The dependence of luminescence intensity on temperatures (25–150 °C) was measured. The chromaticity coordinates and activation energy (ΔE) for thermal quenching were reported. The phosphor shows an excellent thermal stability on temperature quenching.Highlights► Eu2+-activated K4CaSi3O9 shows a broad excitation extending from 250 to 450 nm. ► The phosphor presents bright yellowish-green color for the near UV excitation. ► There are two Eu2+ luminescence centers at 530 nm and 586 nm in K4CaSi3O9 lattices. ► K4CaSi3O9:Eu2+ has an excellent thermal stability with activation energy 0.161 eV.

Er3+-doped 0.75PMN–0.25PT transparent ceramic was synthesized by the two-step sintering method. The optical transmittance, absorption, excitation and emission spectra were investigated. The influence of temperature on the infrared luminescence intensity and emission FWHM (full width at half maximum) was studied. The typical 4I13/2 → 4I15/2 emission transition bands of Er3+ ions at around 1553 nm have been observed in a wide temperature range from 300 K to 12 K. With increasing temperature from 12 to 185 K the luminescence intensity is considerably enhanced and then decreased up from 185 K to 300 K with pronounced broadening of all bands.Highlights► Er3+-doped 0.75PMN-0.25PT transparent ceramic was synthesized. ► The optical transmittance, absorption and band gap energy were investigated. ► The detailed infrared luminescence properties were firstly reported.

Eu2+-activated LiBaPO4 phosphor was synthesized by conventional solid-state reaction. The photoluminescence excitation and emission spectra, the temperature dependent luminescence intensities (12−450 K), and decay curves of the phosphor were investigated. With the increasing of temperatures, the emission bands of LiBaPO4:Eu2+ show the abnormal blue-shift and the decreasing of emission intensity. The natures of the Eu2+ emission in LiBaPO4, for example, the luminescence quenching temperature, and the activation energy for thermal quenching (ΔE), were reported. The afterglow fluorescence was detected in LiBaPO4:Eu2+ phosphor. Together with the Eu2+ luminescence, Eu3+ ions with the abnormal crystal field were observed. The site-selective excitation in the 5D0 → 7F0 region for Eu3+ ions, emission spectra, and decay curves have been investigated using a pulsed, tunable, and narrowband dye laser to detect the microstructure and crystallographic surrounding of Eu3+,2+ at Ba2+ sites in LiBaPO4. The multiple sites structure of Eu2+ and Eu3+ ions in LiBaPO4 lattices was suggested. The lower quenching temperature, afterglow, and luminescence mechanism were discussed. The photoluminescence quantum efficiencies of LiBaPO4:Eu2+ were measured and compared with the reported phosphors. Different from the published data on LiBaPO4:Eu2+, this investigation indicates that LiBaPO4:Eu2+ is not a good phosphor candidate applied in white light emitting diode.Keywords: LED; luminescence; optical materials and properties; phosphors; tridymite structure;

Mn2+-doped phosphates Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the emission and excitation spectra, and decay measurements were employed to characterize the synthesized phosphors. The XRD patterns show that Na2CaMg1−xMnx(PO4)2 (x = 0.05–0.3) forms the single low temperature monoclinic phase α-Na2CaMg(PO4)2 with the crystal group of P21/c (No.14). The heavily Mn2+-doped Na2CaMg1−xMnx(PO4)2 (x = 0.6–1.0) crystallizes in the single high-temperature trigonal phase of β-Na2CaMg(PO4)2 with space-groupPm1 (No. 164). The members with x = 0.3–0.5 form a series of solid solutions containing two distinct phases, α- and β-Na2CaMg(PO4)2. The dependence of luminescence spectra on the Mn2+-doping concentration in Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) was investigated. The great red-shift of Mn2+ emission with increasing Mn2+-concentration in Na2CaMg(PO4)2 were observed. The results are discussed in relation with the detailed crystal structure and the spectral analyses. The CIE coordinates and the luminescence decay (lifetimes) of Mn2+ ions were discussed in order to further investigate the potential applications.

Eu3+ doped red-emitting phosphors of double phosphates Ca9R(PO4)7 (R = Al, Lu) were synthesized by a general high temperature solid-state reaction. The phosphors were characterized by X-ray powder diffraction (XRD). The detailed luminescence properties, e.g., the emission spectra under the excitation of UV light, the photoluminescence excitation spectra and decay lifetimes were reported. The phosphors can be efficiently excited by near UV light to realize an intense red luminescence (613 nm) corresponding to the electric dipole transition 5D0 → 7F2 of Eu3+ ions. The luminescence properties and the potential applications were analyzed. These phosphors were investigated by the site-selective emission spectra and the fluorescence decay curves in the 5D0 → 7F0 region using a pulsed, tunable, narrowband dye laser. It is suggested that Eu3+ ions have three different crystallographic sites doped in Ca9Al(PO4)7, and five sites in Ca9Lu(PO4)7 host. The site assignments of Eu3+ ions in Ca9R(PO4)7 (R = Al, Lu) were discussed on the base of both optical spectroscopy results and structural analysis.

Eu2+-doped monophosphates NaSrPO4 and KBaPO4 with the β-K2SO4 structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay curves were measured. The phosphors can be efficiently excited by UV−visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu2+ emission, e.g., the chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO4:Eu2+ and KBaPO4:Eu2+ were obtained from the temperature dependent (10−435 K) luminescence intensities and decay curves. KBaPO4:Eu2+ presents only one emission center; however, Eu2+ ions have a “disordered environment” in NaSrPO4 lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu3+ ions in the 7F0→5D0 transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO4, the Eu3+ ions could be distributed in the host with a high “ordered state” in only one site in the lattices. However, the multiple site structure of Eu3+ ions with highly disordered distributions in NaSrPO4 lattices was suggested.

A red-emitting phosphor, Eu3+-doped Ca9LiGd2/3(PO4)7, was synthesized by the conventional high-temperature solid-state reaction. X-ray powder diffraction (XRD) analyses confirmed the pure crystalline phase of Whitlockite-type structure. The excitation spectra of Eu3+ doped Ca9LiGd2/3(PO4)7 were measured in the VUV and UV region indicating an efficient energy transfer process from the host and Gd3+ to Eu3+ ions. Upon excitation with VUV and UV radiation, the phosphor showed strong red emission around 611 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu3+ ions. The VUV- and UV-excited luminescence spectra of Ca9LiGd2/3(PO4)7:Eu3+ together with the dependence of the integrated emission intensities on the doping levels were investigated. The Eu3+ ions were investigated by a tunable laser as an excitation source. The excitation spectra of 7F0→ 5D0 transitions suggest that there are two families of inequivalent sites for Eu3+ in this host. The concentration quenching and crystallographic site-occupancy of Eu3+ ions in Ca9LiGd2/3(PO4)7 host were discussed on the basis of the site selective excitation and emission spectra, the luminescence decay and its crystal structure.

A new phosphor of Eu2+-doped Cs2MgSi5O12 was synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra were measured. The phosphor presents bright yellowish-green-emitting luminescence. The site-occupancy of Eu2+ ions doped in Cs2MgSi5O12 was discussed according to the crystal structure and the luminescence characteristics of Eu2+ ions. Two different Eu2+ centers were assigned in Cs2MgSi5O12 lattices. The dependence of luminescence intensity on the heating temperatures was measured and discussed. The chromaticity coordinates and activation energy (ΔE) for the thermal quenching of Cs2MgSi5O12:Eu2+ were reported.

Zr4+- and Eu3+-codoped SrMg2(PO4)2 phosphors were prepared by conventional solid-state reaction. Under the excitation of ultraviolet light, the emission spectra of Sr0.95Eu0.05Mg2−2xZr2xP2O8 (x = 0.0005–0.07) are composed of a broad emission band peaking at 500 nm from Zr4+-emission and the characteristic emission lines from the 5D0 → 7FJ (J = 0, 1, 2, 3 and 4) transitions of Eu3+ ions. These phosphors show the long-lasting phosphorescence. The emission color varies from red to white with increasing Zr4+-content. The white-light emission is realized in single-phase phosphor of Sr0.95Eu0.05Mg2−2xZr2xP2O8 (x = 0.07) by combining the Zr4+- and Eu3+-emission. The duration of the persistent luminescence of Sr0.95Eu0.05Mg2−2xZr2xP2O8 (x = 0.07) reaches nearly 1.5 h. The time at which the long-lasting phosphorescence intensity is 50% of its original value (T0.5) is 410 s. The afterglow decay curves and the thermoluminescence spectra were measured to discuss this long-lasting phosphorescence phenomenon. The co-doped Zr4+ ions act as both the luminescence centers and trap-creating ions.

Ce3+-doped Na2CaMg(PO4)2 was prepared by high temperature solid-state reaction. The phosphor was confirmed to be pure crystalline phase of Na2CaMg(PO4)2. The spectroscopic properties of the Ce3+ ions were investigated by vacuum ultraviolet spectroscopy. The energy transfer from the host to Ce3+ ions was demonstrated. The phosphor could be excited by VUV light and showed a broad purplish blue emission with the maximum wavelength at 385 nm. The five 5d levels corresponding to the 4f1 → 4f05d1 transition of Ce3+ ions were identified. The spectroscopic parameters, e.g., the barycenter, host absorption bands, crystal field splitting and stokes shift were discussed.

Sm2+-doped strontium borophosphate, Sr6BP5O20, was prepared by high-temperature solid-state reaction method. The photoluminescence excitation and emission spectra together with the decay curves of Sm2+ ions were investigated from 10 to 300 K. The emission arises from the 5D0 level of Sm2+ ions. The investigations were focused mainly on the distribution of Sm2+ sites in Sr6BP5O20 crystal, which exhibits different spectroscopic features. There exist two isolated Sm2+ crystallographic sites in Sr6BP5O20 at low temperature (10 K), where no energy transfer could be detected. Only one Sm2+ site could be detected at high temperature above 100 K. Luminescence and microstructure of Sm2+ ions were discussed based on the structure of Sr6BP5O20 crystal.

The fully concentrated Eu3+-based molybdenum borate Eu2MoB2O9 was synthesized by the solid-state reaction method. The photoluminescence excitation and emission spectra, the temperature dependent luminescence intensities and the decay curve were investigated. Photoluminescence spectra show that the phosphor can be efficiently excited by near-UV light and exhibits an intense red luminescence corresponding to the electric dipole transition 5D0 → 7F2 at 615 nm. The luminescence intensities and color purity were investigated by increasing the fired temperatures. The phosphor shows the stable luminescence and color purity at high temperature.

A vanadate, Ca9Dy(VO4)7, was synthesized by the general high temperature solid-state reaction in air atmosphere. X-ray powder diffraction analysis confirmed the formation of single phase Ca9Dy(VO4)7. Photoluminescence excitation spectrum showed that the phosphor could be efficiently excited by UV–visible light from 250 to 500 nm. The characteristic emission peaks of Dy3+ were observed in the emission spectra due to the transitions of 4F9/2 → 6H15/2 at 483 nm and 4F9/2 → 6H13/2 at 573 nm. The photoluminescence measurements showed that the Ca9Dy(VO4)7 exhibited an improved chromaticity compared with YVO4:Dy3+. This was ascribed to lower site symmetry and disordered cation sites in Ca9Dy(VO4)7. The luminescence characteristics of Ca9Dy(VO4) indicated that this phosphor has a possible application for white-light-emitting diode. Luminescence mechanism and site occupancies of Dy3+ ions in Ca9Dy(VO4)7 lattices were discussed.

Eu2WO6 was synthesized by the conventional solid state reaction method. Crystal phase was characterized by the X-ray powder diffraction. The excitation and emission spectra indicate that this phosphor can be effectively excited by near UV (395 nm) and blue light (465 nm), and the emission spectra exhibit a satisfactory red performance at 611 nm, which is due to the characteristic 5D0−7F2 transitions of Eu3+ ions. The luminescence intensities and color purity were investigated by increasing the fired temperature. The phosphor shows stable luminescence and color purity at high temperature.

The Sm3+-doped alkali strontium borate glass-ceramics were obtained by heating of the as-made glasses in air, where Sm3+ ions were reduced to Sm2+ ions. The XRD, optical absorption spectra and luminescence of Sm3+ and Sm2+ ions were investigated. The excitation spectra of the 7F0 → 5D0 transition were measured in the region of 7F0 → 5D1 transition, where spectral holes were burnt within two of the Stark split 5D1 bands. The Sm2+ ions doped glass ceramics exhibit the persistent spectral hole burning at room temperature. The hole depth, which are burned by the DCM dye laser, are about 40% of the total intensity, respectively. It is concluded that the dominant burning mechanism is a photoionization of electron trapping at a site other than Sm3+ ions because of the absence of an antihole around the burned hole.

In this experiment, strontium borate glasses were prepared using the conventional quenching method in air atmosphere. Optical absorption, photoluminescence excitation and emission spectra, X-ray excited luminescence (XEL), and luminescence decay curve of the as-prepared glasses were investigated at room temperature. The as-prepared glasses had two kinds of Eu ions, i.e., Eu2+ and Eu3+. Compared with the reported results of strontium borate glasses, Eu2+ luminescence was enhanced in the studied strontium borate glasses coprepared with F− and Li+ ions. The coexisting of Li+ or F− in the borate glasses could create more negative defect VSr? and stabilize Eu2+ ions, which might act as donor of electrons; For the F− doping, the new center of B(O, F)4 (or BO3F) and BO2F2 units could be considered to be the distorted (BO4), which were needed as a rigid framework to stabilize the divalent rare earth ions.

•A2NiWO6 (A = Ca, Sr) nano-perovskite were prepared via the sol–gel method.•The crystalline crystal structure was refined.•The optical absorption and band structure were clarified.•The photocatalysis activities were discussed on structural properties.A2NiWO6 (A = Ca, Sr) double perovskite semiconductors were prepared via the sol–gel method. The crystal phases were confirmed via X-ray powder diffraction (XRD) measurements together with Rietveld refinements. The morphological and chemical properties of the samples were investigated by the scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and the specific surface area measurements. The optical absorptions and the band structures of the two double perovskites were discussed based on the on the experimental results and theoretical calculation. The d–d allowed transitions in Ni2+–O octahedra have great contributions to the narrow band-gap. The Ni2+-containing tungstate perovskites were potential photocatalysts, which are efficient for its photodegradation for methylene blue (MB) under the irradiation of visible light (λ> 420 nm). The photocatalytic activities were attributed to the special structure properties and multivalent Ni and W ions in the perovskite lattices.Download high-res image (144KB)Download full-size image

•Ni-doped Cu2(OH)3Cl were successfully prepared by a hydrothermal synthesis.•Paratacamite phase can be well stabilized by Ni-doping at ambient temperature.•Band gap is narrowed and conduction band becomes dispersion on Ni-doping.•Ni-doping improves photocatalytic abilities of paratacamite phase Cu2(OH)3Cl.Ni-doped Cu2(OH)3Cl microcrystals were prepared by a facile hydrothermal synthesis without the help of any additive inorganic or organic reagent. The micro-particles were investigated by X-ray powder diffraction (XRD) with Rietveld refinement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis optical absorption, and X-ray photoelectron spectroscopy (XPS) etc. Ni-doping could well stabilize the Cu2(OH)3Cl paratacamite phase at ambient temperature. The band structure and energy positions of Ni-doped Cu2(OH)3Cl microparticles were investigated. The band gap of Cu2(OH)3Cl could be greatly decreased by Ni-doping. The conduction band bottom of Ni-doped Cu2(OH)3Cl is lower and possesses greater dispersion than that of pure Cu2(OH)3Cl. The photocatalytic activity of Ni-doped Cu2(OH)3Cl micro-particles was evaluated by the photodegradation of Rhodamine B (RhB) dye under visible-light irradiation. The Ni-doping increases the photocatalytic activity of Cu2(OH)3Cl. The photocatalytic activity was discussed on the base of the structural and electronic characteristics.Download high-res image (187KB)Download full-size image

The concentration effect on the photoluminescence (PL) of the praseodymium Pr3+ ion is studied at 298–12 K for barium gadolinium molybdate (BaGd2(MoO4)4, called BGM) crystals with a wide Pr3+ concentration range of 0.05–25.0 mol%. Three types of concentration dependences are observed for the emissions although all types show PL quenching at high concentrations. The first type (Type A) has the maximum PL intensity at about 10 mol% with a non-zero intensity at high concentrations, which is observed for the 3P0 emissions except for emission at 621 nm. The second and third types (Type B-1 and B-2) have the maximum at about 1 mol% with a finite residual intensity and nearly zero intensity at high concentrations, respectively, which are observed for the 621 nm emission and all the 1D2 emissions. It is suggested that the energy migration mechanism is responsible for Type A, while the non-resonant cross-relaxation is responsible for Type B-1 and the resonant cross-relaxation for Type B-2.

A red-emitting phosphor, Eu3+-doped Ca9LiGd2/3(PO4)7, was synthesized by the conventional high-temperature solid-state reaction. X-ray powder diffraction (XRD) analyses confirmed the pure crystalline phase of Whitlockite-type structure. The excitation spectra of Eu3+ doped Ca9LiGd2/3(PO4)7 were measured in the VUV and UV region indicating an efficient energy transfer process from the host and Gd3+ to Eu3+ ions. Upon excitation with VUV and UV radiation, the phosphor showed strong red emission around 611 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu3+ ions. The VUV- and UV-excited luminescence spectra of Ca9LiGd2/3(PO4)7:Eu3+ together with the dependence of the integrated emission intensities on the doping levels were investigated. The Eu3+ ions were investigated by a tunable laser as an excitation source. The excitation spectra of 7F0→ 5D0 transitions suggest that there are two families of inequivalent sites for Eu3+ in this host. The concentration quenching and crystallographic site-occupancy of Eu3+ ions in Ca9LiGd2/3(PO4)7 host were discussed on the basis of the site selective excitation and emission spectra, the luminescence decay and its crystal structure.

Eu2+- and Eu3+-doped MgZn2(PO4)2 were prepared using the high temperature solid-state reaction method. The excitation spectra in the UV and VUV region, the emission spectra, and the luminescence decay curves of the Eu2+ and Eu3+ ions were investigated. The crystallographic distributions of the Eu2+ and Eu3+ sites in MgZn2(PO4)2 lattices are different. MgZn2(PO4)2:Eu2+ presents a bluish green luminescence with two distinct emission centers at 450 and 525 nm. MgZn2(PO4)2:Eu3+ presents an reddish orange color with luminescence transitions from the 5D0 level of the Eu3+ ions. There exist two Eu2+-crystallographic sites in MgZn2(PO4)2:Eu2+, which occupy both Mg2+ and Zn2+ sites. However, there is only one Eu3+-site in the MgZn2(PO4)2:Eu3+ lattices, which was confirmed by site-selective excitation and emission spectroscopy, and the luminescence decay in the 5D0 → 7F0 region of the Eu3+ ions under a pulsed, tunable, narrowband dye laser. The Eu3+ ion was suggested to occupy the octahedral Mg2+-site in the MgZn2(PO4)2 lattices. The spectral characteristics, the temperature-dependent luminescence intensity and activation energies of thermal stabilities and the microstructures were discussed on the basis of the crystal structure and the luminescence results.

Mn2+-doped phosphates Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the emission and excitation spectra, and decay measurements were employed to characterize the synthesized phosphors. The XRD patterns show that Na2CaMg1−xMnx(PO4)2 (x = 0.05–0.3) forms the single low temperature monoclinic phase α-Na2CaMg(PO4)2 with the crystal group of P21/c (No.14). The heavily Mn2+-doped Na2CaMg1−xMnx(PO4)2 (x = 0.6–1.0) crystallizes in the single high-temperature trigonal phase of β-Na2CaMg(PO4)2 with space-groupPm1 (No. 164). The members with x = 0.3–0.5 form a series of solid solutions containing two distinct phases, α- and β-Na2CaMg(PO4)2. The dependence of luminescence spectra on the Mn2+-doping concentration in Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) was investigated. The great red-shift of Mn2+ emission with increasing Mn2+-concentration in Na2CaMg(PO4)2 were observed. The results are discussed in relation with the detailed crystal structure and the spectral analyses. The CIE coordinates and the luminescence decay (lifetimes) of Mn2+ ions were discussed in order to further investigate the potential applications.

Eu3+ doped red-emitting phosphors of double phosphates Ca9R(PO4)7 (R = Al, Lu) were synthesized by a general high temperature solid-state reaction. The phosphors were characterized by X-ray powder diffraction (XRD). The detailed luminescence properties, e.g., the emission spectra under the excitation of UV light, the photoluminescence excitation spectra and decay lifetimes were reported. The phosphors can be efficiently excited by near UV light to realize an intense red luminescence (613 nm) corresponding to the electric dipole transition 5D0 → 7F2 of Eu3+ ions. The luminescence properties and the potential applications were analyzed. These phosphors were investigated by the site-selective emission spectra and the fluorescence decay curves in the 5D0 → 7F0 region using a pulsed, tunable, narrowband dye laser. It is suggested that Eu3+ ions have three different crystallographic sites doped in Ca9Al(PO4)7, and five sites in Ca9Lu(PO4)7 host. The site assignments of Eu3+ ions in Ca9R(PO4)7 (R = Al, Lu) were discussed on the base of both optical spectroscopy results and structural analysis.

The red-emitting Eu3+-doped rare earth antimonates R3SbO7 (R = La, Gd, Y) were prepared by high-temperature solid-state reaction. The crystal-phase formations were verified by X-ray powder diffraction (XRD) and structural refinements. The luminescence properties such as photoluminescence (PL) excitation and emission spectra, fluorescence decay curves, absolute luminescence quantum efficiency (QE), CIE color coordinates and the dependence of luminescence intensity on doping level were investigated. The luminescence QE, CIE color coordinates, and the spectrum characteristics of Eu3+ ions have a strong dependence on both R (La, Gd, Y) cations and Eu3+ doping levels. The 5D0 → 7F4 emission peak at 710 nm was the dominant transition in Eu3+-doped La3SbO7, while 5D0 → 7F0 at 580 nm was the strongest transition in Eu3+-doped Y3SbO7. The luminescence properties were discussed on the basis of the crystal structure. Different Eu3+ luminescence centers, such as isolated centers, pair broadening, and cluster centers, were discussed based on the dependence of the lifetime values on Eu3+ concentration. The luminescence QE of La3SbO7:0.4Eu3+ can reach 63.8% under excitation of UV light at room temperature; thus, it can have potential application as a red-emitting phosphor for solid-state lighting.

CaB2O4 powders and ceramics were prepared by the conventional solid-state reaction. In vitro hydroxyapatite (HA) mineralization was investigated by soaking the samples in simulated body fluid (SBF) for various time periods. X-ray diffraction and structural refinements, scanning electron microscopy and X-ray energy-dispersive spectra measurements were applied to investigate apatite formation before and after immersion in SBF. HA can easily form flower-like nanostructures with nano-needles even when soaked in SBF for several hours. The in vitro bioactivity of CaB2O4 was attributed to easy formation of B–OH groups in the CaB2O4 structure when soaked in SBF solutions. In the process of mineralization, the luminescence evolution of Eu3+ ions, a well-known structural probe, was detected by photoluminescence spectra and photoluminescence decay curves. This suggested that the process of mineralization can be monitored by the luminescence intensity of Eu3+ ions in the mineralization products. The current study will open up a new and simple in vivo avenue for in situ monitoring of hydroxyapatite conversion using a fiber luminescence spectrometer.