Bin Li,Yingfang Li,Bin Cao,Chong Yang,Rongbo Ma,Chaoyong Deng,Weichao Huang
The high-temperature solid-state method synthesized novel double perovskite CaSrLaSbO 6 : Bi 3+ , Mn 4+ phosphors. Its crystal structure, luminescence properties, crystal field strength, energy transfer process, and temperature-sensitive properties were comprehensively investigated. The band gap values of CaSrLaSbO 6 were calculated using density functional theory. In the CaSrLaSbO 6 host, Bi 3+ exhibits multiple emission properties in the violet, blue, and NIR regions due to the 3 P 1 → 1 S 0 transition, while the red emission is due to the 2 E g → 4 A 2g transition of Mn 4+ . Light-converting films fabricated using CaSrLaSbO 6 :Bi 3+ , Mn 4+ under 302 nm UV excitation with multiple emissions showed significant plant growth promotion. In addition, the optical temperature-dependent response of CaSrLaSbO 6 : Bi 3+ , Mn 4+ was analyzed using the luminescence intensity ratio technique, and the relative sensitivity of the best samples reached 2.1 % K −1 . The above results indicate that CaSrLaSbO 6 : Bi 3+ , Mn 4+ provides almost all the light sources necessary for plant growth and can be applied in the field of optical temperature sensors, which shows that this multifunctional phosphor has great potential for application.
ZnTiO 3 :Eu 3+ ,Mn 4+ phosphors with hexagonal and cubic structure are synthesized by solvothermal method. The structure of ZnTiO 3 depends on precursors and the annealing temperature. Inverse spinel Zn 2 TiO 4 phase reveals the highest thermostability compared with cubic ZnTiO 3 and hexagonal ZnTiO 3 phases. The different phases of ZnTiO 3 crystals exhibit different photoluminescence properties. The forbidden transition of 4 A 2 g → 2 T 2 g for Mn 4+ is observed in Zn 2 TiO 4 and hexagonal ZnTiO 3 (h-ZnTiO 3 ) due to the decreased symmetry. The zero photon line (ZPL) assigned to 2 E g → 4 A 2 g transition of Mn 4+ is absent in all type ZnTiO 3 phases. A sharp emission peak at 714 nm assigned to ν 6 (Stokes emission) mode of Mn 4+ in h-ZnTiO 3 is present when the temperature was below 270 K, and increases sharply in intensity with the temperature decreasing. The similar PL spectra of cubic ZnTiO 3 and Zn 2 TiO 4 co-doped with Eu 3+ and Mn 4+ show a wide emission band composed of Stokes and anti-Stokes modes. The calculated nephelauxetic parameter increases from 0.84 to 1.03 and 1.18 for Mn 4+ in h-ZnTiO 3 , cubic ZnTiO 3 and Zn 2 TiO 4 , respectively, indicating the covalency decreasing, which causes the red shift of ZPL in h-ZnTiO 3 . The Mn 4+ emissions show stronger temperature dependence than that of Eu 3+ , especially for that in h-ZnTiO 3 matrix. Based on the fluorescence intensity ratio between I Eu 3+ and I Mn 4+ , the highest relative temperature sensitivity of 2.46 %K −1 is observed in cubic ZnTiO 3 (c-ZnTiO 3 ) and Zn 2 TiO 4 . Under the excitation at 550 nm, the highest relative sensitivity of 2.9 %K −1 is achieved in c- and h-ZnTiO 3 mixed phases.
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