This study reports the first integration of inorganic tantalum octahedral metal atom clusters into multifunctional nanocomposite coating materials and devices for window technology and energy saving applications. [Ta6Bri12]n+ (n = 2, 3 or 4) cluster-based high visible transparency UV and NIR filters are realized. Green and brown colored films are fabricated by coating on an indium-doped tin oxide glass substrate by electrophoretic deposition, an industrialized solution process. The efficiency in energy saving of the new UV-NIR filters was estimated by the determination of different figure of merit (FOM) values, such as Tvis, Tsol and Tvis/Tsol (Tsol = solar transmittance and Tvis = visible transmittance), and the color coordinates (x, y, z and L*a*b). The Tvis/Tsol ratio is equal to 1.25 for the best films. Such values are evidence of a higher energy saving efficiency than most of the inorganic composites reported in the literature. These promising results pave the way for the use of transition metal clusters as a new class of nanocoatings in energy saving window-based applications.

A red phosphor of Sr2Si5N8:Eu2+ powder was synthesized by a solid state reaction. The synthesized phosphor was thermally post-treated in an inert and reductive N2–H2 mixed-gas atmosphere at 300–1200 °C. The main phase of the resultant phosphor was identified as Sr2Si5N8. A passivation layer of ∼0.2 μm thickness was formed around the phosphor surface via thermal treatment. Moreover, two different luminescence centers of Eu(SrI) and Eu(SrII) in the synthesized Sr2Si5N8:Eu2+ phosphor were proposed to be responsible for 620 nm and 670 nm emissions, respectively. More interestingly, thermal- and moisture-induced degradation of PL intensity was effectively reduced by the formation of a passivation layer around the phosphor surface, that is, the relative PL intensity recovered 99.8% of the initial intensity even after encountering thermal degradation; both moisture-induced degraded external and internal QEs were merely 1% of the initial QEs. The formed surface layer was concluded to primarily prevent the Eu2+ activator from being oxidized, based on the systemic analysis of the mechanisms of thermal- and moisture-induced degradation.

The red phosphor of Sr2Si5N8:Eu2+ was synthesized by a solid state reaction. The as-synthesized phosphor powders were post-treated in a N2 atmosphere. The prepared samples were analyzed by XRD, FE-SEM, TG-DTA, FT-IR, zeta potential, cathodoluminescence (CL), photoluminescence (PL), quantum efficiencies (QEs), and temperature-dependent PL and QE techniques. After the thermal treatment in N2, it was found that the N2-treatment caused a negligible influence on the phase purity and particle morphology; the surface of the phosphor particle became more hydrophilic; the isoelectric point (IEP) of the suspension containing phosphor powder shifted to a higher pH value; the edge area (formed surface layer) of the phosphor particle had lower CL intensity than the inner part but it inhibited the surface damage caused by e-beam irradiation; more significantly, the formed surface layer plays a passivating role in preventing the Eu2+ activator from being oxidized, consequently, effectively reducing thermal degradation that deteriorates the PL intensity of the Sr2Si5N8:Eu2+ phosphor.

Phosphor deposits of β-sialon:Eu2+ were prepared by electrophoretic deposition (EPD) process within a magnetic field. Under the action of the magnetic force, which was parallel to the direction of the electric field of the EPD, the β-sialon:Eu2+ crystals were aligned along the c-axis of the hexagonal cell unit to form an oriented deposit via the EPD fabrication. Higher orientation degree was obtained at longer depositing time (300 s) and stronger applied magnetic field (12 T). The oriented deposit aligned along the c-axis obtained higher relative deposit density than the randomly fabricated deposit. Due to the improved relative density, the oriented deposit prepared within the magnetic field possessed an enhanced external quantum efficiency (ηex). Also, because of different relative densities of the deposits prepared within and without the magnetic field, they presented different chromaticity coordinates.

Highlights•Various A-site deficient LSGMs were prepared by a solid state reaction method.•High temperature reactivity of the A-site deficient LSGM with GDC was investigated.•The introduction of the A-site deficiency effectively suppressed the reactivity.La0.8Sr0.2Ga0.8Mg0.2O3 − δ (LSGM) powders with various types of A-site deficiencies were synthesized and then their reactivities with Ce0.9Gd0.1O3 − δ (GDC) were compared. There were 4 types-12 sorts of prepared powders, i.e., normal LSGM La0.8Sr0.2Ga0.8Mg0.2O2.8; La deficient LSGM; La and Sr deficient LSGM, the La/Sr ratio fixed at 0.8/0.2; the La and Sr deficient LSGM, and the oxygen amount fixed at 2.8. Each of the LSGM powders with different types of A-site deficiencies was mixed with the GDC powder and thermally treated in air. The formation of the reacted phases during the thermal treatment was characterized by comparing their XRD spectra. The XRD patterns indicated that the effect of the suppression of the reactivity of LSGM was clearly confirmed; the effect is much more remarkable by keeping the oxygen amount the same as LSGM8282 (oxygen amount = 2.8). The most reaction-suppressed sample was La0.9Sr0.05Ga0.8Mg0.2O2.8 (A-site cation = 0.95, O = 2.8). The electric measurement revealed that the La0.9Sr0.05Ga0.8Mg0.2O2.8 exhibited a low chemical reactivity with GDC, while maintaining a modest level of electric conductivity.

The compaction of a Eu-doped Ca-α-SiAlON phosphor powder was performed by electrophoretic deposition (EPD). The effect on the adhesion and optical properties of the silica precursor as both a binder of the powder and a filler of the air voids were evaluated. The adhesion of the silica impregnated composite film to the silica glass substrate was characterized by the tape test. The improvement of the external quantum efficiency was confirmed from the PL spectra measurement after the silica impregnation. The temperature dependence of the external quantum efficiency was also investigated in order to discuss the advantage of using the silica precursor as a binder for high-brightness LED applications.

A red phosphor of Sr2Si5N8:Eu2+ powder was synthesized by a solid state reaction. The synthesized phosphor was thermally post-treated in an inert and reductive N2–H2 mixed-gas atmosphere at 300–1200 °C. The main phase of the resultant phosphor was identified as Sr2Si5N8. A passivation layer of ∼0.2 μm thickness was formed around the phosphor surface via thermal treatment. Moreover, two different luminescence centers of Eu(SrI) and Eu(SrII) in the synthesized Sr2Si5N8:Eu2+ phosphor were proposed to be responsible for 620 nm and 670 nm emissions, respectively. More interestingly, thermal- and moisture-induced degradation of PL intensity was effectively reduced by the formation of a passivation layer around the phosphor surface, that is, the relative PL intensity recovered 99.8% of the initial intensity even after encountering thermal degradation; both moisture-induced degraded external and internal QEs were merely 1% of the initial QEs. The formed surface layer was concluded to primarily prevent the Eu2+ activator from being oxidized, based on the systemic analysis of the mechanisms of thermal- and moisture-induced degradation.

The red phosphor of Sr2Si5N8:Eu2+ was synthesized by a solid state reaction. The as-synthesized phosphor powders were post-treated in a N2 atmosphere. The prepared samples were analyzed by XRD, FE-SEM, TG-DTA, FT-IR, zeta potential, cathodoluminescence (CL), photoluminescence (PL), quantum efficiencies (QEs), and temperature-dependent PL and QE techniques. After the thermal treatment in N2, it was found that the N2-treatment caused a negligible influence on the phase purity and particle morphology; the surface of the phosphor particle became more hydrophilic; the isoelectric point (IEP) of the suspension containing phosphor powder shifted to a higher pH value; the edge area (formed surface layer) of the phosphor particle had lower CL intensity than the inner part but it inhibited the surface damage caused by e-beam irradiation; more significantly, the formed surface layer plays a passivating role in preventing the Eu2+ activator from being oxidized, consequently, effectively reducing thermal degradation that deteriorates the PL intensity of the Sr2Si5N8:Eu2+ phosphor.