Phase transition in Smsub(0.8)Gdsub(0.2)S alloy at low temperature

The transition from a semiconductor phase B' into metal phase M and back again has been studied for the Smsub(0.8)Gdsub(0.2)S alloy by X-ray analysis. The experiments have been carried out with single crystal and powder samples in the range of temperatures from 110 K to 293 K. The M → B' transition at approximately 147 K is accompanied with the single crystal failure. The graphs show variation of the alloy lattice parameter with temperature. The MreversibleB' transition takes place in the range of 30K. The linear dependence of the amount of a new phase on the temperature in MreversibleB' transition is obtained. The 'anomalous' part of the lattice parameter variation with temperature a(T) is discriminated. It has been supposed that Sm ions in the M phase are two states: in Sm2+ and in a 'mixed' hybridized state with an intermediate valency. Apparently, the 'anomalous' growth of a(T) below 200 deg K is due to the Sm2+ ion increasing number