Outstanding pure green upconversion luminescence in LaZrTa3O11:Er3+/Yb3+ phosphors prepared by molten salt synthesis with B2O3 flux

Hexagonal Er 3+ /Yb 3+ co-doped LaZrTa 3 O 11 (LZTO) phosphor was prepared by molten salt synthesis with B 2 O 3 flux. Holding temperature, holding time, solute and solvent ratio were regulated. The green upconversion luminescence (UCL) integral intensity of the optimal sample can reach 29.2% of β-NaYF 4 :Er 3+ /Yb 3+ under 980 nm laser excitation. This outstanding pure green UCL is due to the low phonon energy, Er 3+ /Yb 3+ monolayer (2D) distribution, asymmetry of Er 3+ /Yb 3+ doped lattice sites, and low oxygen vacancy. The maximum relative temperature sensitivity attains 0.01221 K −1 at 303 K by employing luminescence intensity ratio (LIR) technique. LZTO:Er 3+ /Yb 3+ phosphor can be used in temperature sensing.