Effects of phase structure on up-conversion photoluminescence and dielectric performance in Er3+ doped (Bi0. 5Na0. 5)TiO3-BaTiO3 lead-free ceramics

The effects of phase structure on up-conversion (UC) photoluminescence (PL) and dielectric properties of lead-free ceramics of Er3+-doped x (Bi0·5Na0.5)TiO3-(1-x)BaTiO3 (xNBT-BT: Er3+, 0.00 ≤ x ≤ 0.90) were investigated. X-ray diffraction and Rietveld structural refinement analyses were conducted to characterize the phase structure. On increasing the NBT concentration, the crystal structure changes from tetragonal P4mm to P4bm phase. The UC emission is significantly enhanced with the increment of tetragonality, while it begins to decrease upon the occurrence of the P4bm phase. Temperature-dependent UC emission spectra have shown that the optimal emission sample of 0.70NBT-BT: Er3+ exhibits a high color-tuning performance (from green to red). Furthermore, an outstanding thermal stability of UC green emission (65.6% of the initial intensity at 483K) was achieved. The intensity ratio of UC green emission was adopted to reveal the temperature-sensing properties of xNBT-BT: Er3+ ceramics.