THERMOLUMINESCENCE AND DEFECTS OF SR1-XEUXF2+X SOLID ELECTROLYTES

Thermoluminescence (TL) studies of the Sr1-xEu(x)F2+x mixed system hav e revealed three groups of TL glow peaks in the temperature ranges (34 0, 360-370 K), (460-475, 540-575 K) and (615-635, 680-720 K). The TL e mission spectrum of SrF2 consists of two emission bands at 475 and 700 nm, whereas in Sr1-xEu(x)F2+x additional TL emission bands are obtain ed at 418, 500, 580 and 745 nm. Electron-beam-irradiated Sr1-xEu(x)F2x showed optical absorption bands at 265, 464 and 500 nm (x = 0), whil e in other compositions these are suppressed, resulting in additional bands at 226, 328, 345, 355, 365 and 385 nm. The intensity of the 370 K glow peak increases with increasing europium concentration. Room-tem perature annealing also caused an increase in the intensity of the 370 K glow peak. Upon comparison of TL, TL emission, optical absorption a nd room-temperature annealing studies, the 370, 460 and 550 K glow pea ks were attributed to radiative impurity luminescent centers and radia tive recombination of electrons with holes being deexcited from two st ages of F-centers. The corresponding TL emissions are at 475 and 700 n m. The TL emission bands of Sr1-xEu(x)F2+x at 418 nm and at 500, 550, 580 and 745 nm are the characteristic emissions of Eu2+ and Eu3+, resp ectively, and a tentative energy-level diagram is proposed.