Energy dependence of radioluminescence spectra from strontium titanate

Abstract X-ray excited luminescence spectra of strontium titanate are reported over the temperature range from 20-300 K. The range includes several crystalline phases, each with different emission spectra. The signals are thermally quenched above ~220 K. There are spectral shifts and intensity changes around the temperatures associated with phase changes and overall there are nominally three spectral emission bands. A remarkable observation is that at fixed lower temperatures the spectra undergo major changes with the energy of the X-rays. A possible cause of the effect is discussed in terms of inner shell excitation from the K shell of the strontium. Comparisons with thermoluminescence spectra from the strontium titanate are reported.