Effect of thermal synthesis temperature on up-conversion properties of lithium doped Bi3.46Ho0.04Yb0.5Ti3O12: 0.05Li phosphors

•UC, XPS, DRS spectra, luminescence decay and energy transfer of BHYTO: 0.05Li phosphors were discovered systemly.•Sintering temperature has important influence on the UC luminescence of BHYTO: 0.05Li.•Increased grain size induced by thermal effects play an critical role on emission enhancement of BHYTO: 0.05Li.•Increased defects sintered at high temperature such as Bi and O vacancies degraded the UC luminescence. The effects of different sintering temperatures on the structure and upconversion luminescent properties of Li+ doped Bi3.46Ho0.04Yb0.5Ti3O12: 0.05Li (BHYTO: Li) phosphors were investigated. The upconversion emission intensity first increases and then decreases with the increase of sintering temperature from 700 to 1000 °C. The temperature induced grain growth contributes to the enhancement of UC luminescence, but the increased defects such as Bi and O degrade the luminescence. The combined effect of them makes the optimal luminescence appears in the specimens sintered at 800 °C, which is about 2 times stronger than that of those specimens sintered at 700 and 1000 °C. The mean lifetime for the specimens sintered from 700 to 1000 °C increases monotonically from 60.2 to 81.5 μs, with band gap (Eg) from 2.8 to 3.0 eV. The maximal quantum efficiency can reach 0.28 % due to enhanced crystallinity.