Enhancing upconversion luminescence intensity of BiTa7O19:Er3+/Yb3+/Mo4+/Sb by doping Gd3+, La3+ or Lu3+

Abstract

Based on the previous optimal concentration of Er³⁺/Yb³⁺/Mo⁴⁺/Sb co-doped BiTa₇O₁₉ (BTO), Gd³⁺, La³⁺ or Lu³⁺ is planned to be doped into BTO: Er³⁺/Yb³⁺/Mo⁴⁺/Sb for further improving the upconversion luminescence (UCL) intensity under 980 nm laser excitation. These samples are prepared by solid phase sintering. The green UCL integral intensity of Gd³⁺, La³⁺ or Lu³⁺ doping samples reaches 2.87, 2.67 and 2.52 times than that of β-NaYF₄:Er³⁺/Yb³⁺, respectively. It can be attributed to the change in Er³⁺/Yb³⁺ doped site’ symmetry, bandgap increases and local structure changes. The maximum absolute sensitivity (S_A) and relative sensitivity (S_R) is got as 0.01098 K^− 1 at 356 K and 0.00776 K^− 1 at 303 K, respectively. Gd³⁺, La³⁺ or Lu³⁺ doping BTO: Er³⁺/Yb³⁺/Mo⁴⁺/Sb can be applied in luminescence display and temperature sensing.