Lead-free ferroelectric [(Bi0.5Na0.5)0.94Ba0.06]1−xLaxTiO3 (BNBT-100xLa, 0≤x≤0.05) ceramics were prepared by the solid state sintering methods and the effects of La3+ doping on ferroelectricity and electromechanical strain were systematically investigated. The X-ray diffraction analysis revealed that the crystal structure partly transformed from rhombohedral phase to tetragonal phase with the increasing of La3+ donor doping. The long-range FE order dominant in pure BNBT was disrupted by La3+ doping. For BNBT-3La, the largest maximum strain Smax was 0.53% with a high normalized strain d*33 of 707 pm/V under 75 kV/cm at room temperature. Moreover, a phase transition happened at EF=46.06 kV/cm under the cycle of 75 kV/cm. In particularly, a slim and pinched P-E loop was obtained for BNBT-5La with a large energy density of 1.66 J/cm3 at 105 kV/cm.

Octahedron-like KLa1−xEux(MoO4)2 were successfully synthesized by a molten salt sintering method using KCl as flux. The as-prepared products were characterized by X-ray powder diffractometry, scanning electron microscope, high resolution transmission electron microscopy (HRTEM), selected-area electron diffraction and photoluminescence spectrometry. The results show the impact on the morphology is not affected by doping Eu3+. The results of SEAD, HRTEM and EDS shows the microstructure feature of the sample which showed the existence of concentration gradient of Eu3+ in this sample. The emission spectra recorded for an excitation wavelength at 394 nm exhibit a strong emission peak at 616 nm, corresponding to the 5D0→7F2 transition of Eu3+. The commission international Del’Eclairage chromaticity coordinates of the phosphors were about (0.6637, 0.3360) and it is very close to the standard red chromaticity of NTSC. Therefore, the phosphors could be promising for white light-emitting diodes.

Lead-free (1−x)(0.75Bi0.5Na0.5TiO3–0.25Bi0.5K0.5TiO3)–xBiAlO3 (BNT–BKT–100xBA, x=0–0.10) ceramics were prepared by two-step sintering method and their phase structure, micro morphology and electrical properties were systematically investigated. X-ray diffraction analysis indicates a pure perovskite phase for x≤0.06 as well as a structural evolution from a tetragonal toward a pseudocubic phase. Transmission electron microscopy study of the x=0.04 composition reveals the existence of antiferroelectric phase with a0a0c+ oxygen octahedron tilting which is in the form of nano-domains. Polarization-electric field and current-electric field hysteresis loops demonstrate that the increase of BA concentration destroys the ferroelectric order and strengthens antiferroelectric order. A much enhanced energy storage density of 1.15 J/cm3 and efficiency of 73.2% is achieved under 105 kV/cm at x=0.06. In addition, its energy storage property is found to depend weakly on temperature within the measurement range of 25–150 °C.

BiAlO3-doped Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BA-doped BNT-BKT) ceramics are greatly concerned due to their sufficient electric-field-induced strain with small hysteresis and remnant strain for high precision positioning devices and other actuators. In this paper, the structural analysis especially the high-resolution transmission electron microscope (HRTEM) is used to reveal the origin of excellent properties obtained in 0.96(0.75BNT-0.25BKT)-0.04BA, which exhibits a large strain of 0.21% at ∼70 kV/cm, a small strain hysteresis of only 24% and a near-zero remnant strain. Using HRTEM, the antiferroelectric nano-domains composited by three variants of in-phase a0a0c+ octahedral tilting coexisted with the remnant ferroelectric nano-domains of anti-phase a−a−a− octahedral tilting are directly identified. Then a continuous tilting model is proposed to interpret the gradually transitional tilting involving nano-domains leading to the small hysteresis and near-zero remnant strain. The findings may pave a way for further optimizing the properties through creating stable antiferroelectric nano-domains in BNT-based ceramics and the analogues.

Lead-free ferroelectric ceramics (1 − x)[0.94Bi0.5Na0.5TiO3–0.06BaTiO3]–xBaZrO3(BNBT–xBZ, 0 ≤ x ≤ 0.05) were prepared by two-step sintering method, and the effects of BZ doping on phase structure, micro morphology and electromechanical strain were systematically investigated. The X-ray diffraction analysis reveals that the crystal structure transforms from a rhombohedral and tetragonal mixed phase to tetragonal phase with the increasing of BZ doping. The P–E loops and I–E loops demonstrate that the increase of BZ concentration destroys the ferroelectric order and brings about a phase transition from ferroelectric to antiferroelectric. BNBT–0.03BZ exhibits outstanding strain behavior featured by a high strain of 0.33% and a large d33* of 600 pm/V at a moderate electric field of 55 kV/cm at room temperature with a relatively low unipolar strain hysteresis of 32.31%. With the increase of BZ, the value of strain decreases but the hysteresis also becomes lower. When the BZ amount is 0.05 mol%, the value of strain is 0.16% and the unipolar strain hysteresis is 11.30%.

Pb(1–1.5x)Lax(Zr0.66Sn0.25Ti0.09)O3 (x = 0.01, 0.02, 0.03 and 0.04) antiferroelectric ceramics with perovskite structure were prepared by a conventional solid state sintering method. The influences of La content, sintering temperature and soaking time on phase structure and energy-storage density were investigated in detail. The appropriate La content, sintering temperature and soaking time are beneficial for obtaining the homogenous grain size and better energy storage performance. The Pb0.97La0.02 (Zr0.66Sn0.25Ti0.09)O3 ceramics obtained at 1200 °C for 2 h display the optimum electronic performance with the low remnant polarization (1.19 μC/cm2), a large maximum polarization (27.07 μC/cm2) and a large energy density (1.03 J/cm3) at 1 Hz was obtained at a relatively low field (70 kV).

Uniform and well-crystallized orthorhombic YF3:Eu3+ phosphors with different morphologies (rod-like, spindle-like and gearwheel-like) were prepared by a facile microwave-assisted hydrothermal method. The as-synthesized products were systematically characterized by X-ray powder diffractometer (XRD), thermal field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HRTEM), and photoluminescence (PL) spectrometer. The results indicate that reaction temperature and time have great impact on the morphology and size of the products. A possible formation mechanism of the micro-gearwheel like particle was proposed based on the time-dependent experiments and HRTEM results. The emission spectrum recorded for an excitation wavelength of 392 nm exhibited a strongest emission peak centered at 592 nm, corresponding to the magnetic dipole of the 5D0→7F1 transition of Eu3+ ions. The quenching concentration was found at 20 mol% doping of Eu3+. The investigation on morphology-dependent luminescence properties reveals that the gearwheel-like YF3:Eu3+ powders exhibit the strongest orange–red emission, while the intensity of rod-like ones is the lowest.

The emission-tunable CaLa2−xEuxZnO5 phosphors were synthesized by citric sol–gel method. The products were characterized by X-ray diffractometer, scanning electron microscope, energy dispersive spectroscopy and photoluminescence spectrometer. Through adjusting the dopant concentration of Eu3+ in CaLa2ZnO5 phosphor, blue-green to orange-red emission with the 467 nm excitation could be obtained, which matches well with the emission of blue LED chip. Luminescence properties of Ca1−ySryLa1.9Eu0.1ZnO5 (0 ≤ y ≤ 1) indicated that increasing Sr2+ content enhances not only the emission intensity of 5D0 → 7F2 transition but also the emission intensity ratio of 5D0 → 7F2 to 5D0 → 7F1 (asymmetry ratio). The Ca0.6Sr0.4La1.9Eu0.1ZnO5 phosphors possess optimal integrated emission intensity, which is 20 % higher than that of CaLa1.9Eu0.1ZnO5 phosphors, and the Commission International de L’Eclairage chromaticity coordinate is (0.658, 0.341). Ca1−ySryLa2−xEuxZnO5 phosphors may have potential applications in field emission displays based on their particle size, low-cost synthetic route, and diverse luminescent properties.

The development of fluorescent materials with low energy consumption, low cost and desirable optical properties is needed for the perspective of practical application. Here, functional NaLa(MoO4)2@CdTe core–shell microspheres with high fluorescence were prepared by layer-by-layer self-assembly technique. Through the consecutive electrostatic adsorption of charged cetyltrimethyl ammonium bromide and CdTe quantum dots (QDs), the uniform and regular multilayer shell of CdTe QDs was synthesized. The NaLa(MoO4)2@CdTe microspheres exhibited improved photoluminescence intensity and stability of red emission, compared with that of the CdTe QDs powder, and the fluorescence enhancement mechanism were investigated. The CdTe QDs multilayer shell is expected to supersede the Eu3+ ion for producing a novel red phosphor.

•Dense ceramics with impurity phases can be obtained when x ≥ 0.75.•When x ≥ 0.75, two kinds of grain morphologies exist (smooth and rough).•The resistivity and B value increase with the increasing ZnO content.•The addition of ZnO can significantly reduce the aging value.The effect of ZnO addition on the phase composition, morphology, element distribution and electrical properties of Ni0.6Cu0.5ZnxMn1.9−xO4 (0 ≤ x ≤ 1) negative temperature coefficient (NTC) ceramics was studied. The ceramics were crystallized in a single cubic spinel structure when x was 0–0.5, Ni-rich rocksalt and CuO impurity phases were detected at x = 0.75, and ZnO formed at x = 1. The SEM and EDS results showed that the sintered bodies contained two types of grain morphologies, one area was rich in Ni and Cu, the other area was rich in Mn and Zn when x ≥ 0.75. As the Zn content increased, the electrical resistivities and the B25/85 constants of the Ni0.6Cu0.5ZnxMn1.9−xO4 ceramics increased, and they were 11.33–5442.29 Ω cm and 2395–3301 K, respectively. The resistivity drift decreased sharply from 10.2% to 4.8% when x increased from 0 to 0.25, and it reached the lowest value of 0.02% when x = 0.75. The possible reasons are discussed.