Charge transport in silver chalcogenides in the region of phase transition

Data on the sigma(T), R(T), and U(T) dependences in Ag2Te, Ag2Se, and Ag2S in the region of the phase transition are analyzed. It is found that the phase transition in Ag2Te is accompanied by a decrease in the electron concentration and this transition in Ag2Se is accompanied by an increase in this concentration. The concentration of intrinsic charge carriers in Ag2Te decreases by a factor of 4 as a result of the phase transition and increases by a factor of 2 in Ag2Se. The effect of variation in the energy-band parameters in the region of phase transition on the electron mobility is considered. It is established that, in Ag2Te and Ag2S, electrons are scattered by optical phonons in the region of the phase transition, while electrons are scattered by acoustic phonons in the alpha and beta phases. It is assumed that the anomalously large increase in sigma and U in Ag2S as a result of the phase transition is caused by an increase in the concentration n and a simultaneous decrease in epsilon(g) and m(n)* by a factor of about 2.