Wednesday, 31 May 2017: 17:00
Churchill B2 (Hilton New Orleans Riverside)
Ca-based perovskite phosphors activated by rare-earth ions have attracted considerable attention recently as prospective materials for various optoelectronic applications. Crystal structure of Ca-based perovskites is highly distorted from the ideal cubic perovskites as SrTiO3. Thus, strong ff-emissions of rare-earth ions should be derived from low site-symmetry of Ca site. In addition, photoluminescence properties of these phosphors are dependent on not only crystal structure of the host materials, but also preparation condition of the samples. Conventional solid-state reaction (SSR) method is not fit for the synthesis of phosphors with complicated compositions because the degree of cation mixing is relatively low due to slow interdiffusion of the cations. In this study, we investigated the preparation of Pr3+-activated Ca-based perovskite phosphors via an aqueous-solution process using metal complex solutions in order to improve the photoluminescence properties of these phosphors. Pr3+-activated CaTiO3 and CaSnO3 phosphors were prepared by amorphous metal complex (AMC) method using stable water-soluble Ti4+ and Sn4+ complexes coordinated to lactic acid. Especially, we developed a new stable water-soluble Sn4+ complex synthesized from SnCl4·nH2O. Photoluminescence properties of Pr3+-activated CaTiO3 and CaSnO3 under UV irradiation were significantly sensitive for the small deviation of the cation ratios of Ti/Ca and Sn/Ca. When the cation ratios in both the phosphors were less than 1.00, ff-emissions from the phosphors prepared by AMC method were low, compared with the phosphors prepared by SSR method. In contrast, when the cation ratios were precisely controlled from 1.00 to 1.05, ff-emissions of the phosphors prepared by AMC method were higher than those prepared by SSR method. Especially, Pr3+-activated CaSnO3 prepared by AMC method at the optimum condition showed high emission intensity under UV irradiation that was 1.9 times higher than those by SSR method (Fig .1). This work was partially supported by Grant-in-Aid for Scientific Research (C) (no. 15K06445) from MEXT, Japan. This work was also partially supported by the cooperative research program of the “Network Joint Research Center for Materials and Devices”.
