Electronic structure and optical properties of Ti-doped phosphate crystals

摘要

Luminescence properties of NaAl_(1-x) Ti_xP_2O_7 (x=0-1) double phosphates under VUV excitation are studied. Partial densities of electronic states are calculated for perfect NaAlP_2O_7, NaTiP_2O_7 and Ti-doped NaAlP_2O_7 crystals. Pure NaAlP_2O_7 crystals exhibit emission bands peaking near 300 and 770 nm. Doping of NaAlP_2O_7 crystals with Ti ions leads to appearance of emission bands in blue-green spectral region with main peak near 500 nm. NaTiP_2O_7 exhibit emission in blue-green region with similar shape as for NaAlP_2O_7:Ti. The luminescence mechanisms in Ti-doped phosphates are discussed using both experimental and theoretical results. Observed emission bands in blue-green region of spectrum are ascribed to emission centers like Ti~(4+) F-centers.