STRUCTURAL INSTABILITY AND PHOTOCONDUCTION OF TL1-)((TL3+S22)

The structural instability and the photoconduction of mixed-valence co mpounds Tl1+(Tl3+ S22-) are studied by means of X-ray diffraction and photocurrent measurements. From the temperature dependence of observed dark currents and photocurrents, we estimate the band gap energy and discuss the occurrence of thermal quenching as well as possible electr on scattering from both the ferroelectric domain boundaries and the so ft-phonon modes.