Search

Abstract: In this study, we used oxides (Y2O3, CeO2 and Al2O3) as the raw materials to fabricate YAG:Ce3+ phosphors by a molten salt synthesis (MSS) method. The formation of YAG phase strongly depends on the alumina source and firing temperature. Microstructure characterization indicates that “dissolution-precipitation” mechanism dominates the formation process of YAG in the alkali chlorides melt. Thus, highly active nano-Al2O3 starting powders promote their solution in the melt and guarantee a solute stoichiometric of YAG phase rather than other Y–Al–O compounds. The as-prepared YAG:Ce3+ phosphors show typical yellow emission peaked at 535nm under excitation of 460nm blue light, suggesting that MSS could be a promising method for the preparation of phosphor powders even though oxide raw materials are used. [Copyright &y& Elsevier]

Abstract: Ce3+-doped β-SiAlON blue phosphors with composition of Ce x Si6−z Al z O z N8−z (0.2≤z≤4) at a fixed x=0.01 were synthesized by the gas pressure sintering method. The phases and photoluminescence properties were found to be directly correlated to the z value. Higher z value would result in the formation of AlN polytypoid impurity phases. The optimal z value resides in the range 0.3≤z≤0.5, by which high purity of β-SiAlON phase, good crystallinity and fine grain size were obtained, leading to the best luminescence properties. These phosphors could be a good candidate for application in white light-emitting diodes using InGaN-based near–ultraviolet chips. [Copyright &y& Elsevier]

Commercial Y 2 O 3 powder was used to fabricate Y 2 O 3 ceramics sintered at 1600 °C and 1800 °C with concurrent addition of ZrO 2 and La 2 O 3 as sintering aids. One group with different contents of La 2 O 3 (0–10 mol%) with a fixed amount of 1 mol% ZrO 2 and another group with various contents of ZrO 2 (0–7 mol%) with a fixed amount of 10 mol% La 2 O 3 were compared to investigate the effects of co-doping on the microstructural and optical properties of Y 2 O 3 ceramics. At low sintering temperature of 1600 °C, the sample single doped with 10 mol% La 2 O 3 exhibits much denser microstructure with a few small intragranular pores while the samples with ZrO 2 and La 2 O 3 co-doping features a lot of large intergranular pores leading to lower density. When the sintering temperature increases to 1800 °C, samples using composite sintering aids exhibit finer microstructures and better optical properties than those of both ZrO 2 and La 2 O 3 single-doped samples. It was proved that the grain growth suppression caused by ZrO 2 overwhelms the acceleration by La 2 O 3 . Meanwhile, 1 mol% ZrO 2 acts as a very important inflection point with regard to the influence of additive concentration on the transmittance, pore structure and grain size. The highest in-line transmittance of Y 2 O 3 ceramic (1.2 mm in thickness) with 3 mol% of ZrO 2 and 10 mol% of La 2 O 3 sintered at 1800 °C for 16 h is 81.9% at a wavelength of 1100 nm, with an average grain size of 11.2 µm. [ABSTRACT FROM AUTHOR]