Emf induced by a change in the samarium ion valence as a result of a phasetransition in SmS single crystals

The mechanism of the emf appearing in a semiconductor under heating in the absence of external temperature gradients, an effect revealed by the presen t authors, is considered. The experiments were performed on samarium sulfid e (SmS) single crystals. It is shown that the emf is generated by an abrupt change in the samarium ion valence, which results from the ion screening b y the electrons activated into the conduction band. We succeeded in obtaini ng emf pulses 1.3 s long with an amplitude of up to 2.5 V at T similar to 4 60 K, as well as CW emf generation within the 375- to 405-K temperature int erval with a maximum value of similar to 50 mV. (C) 2001 MAIK "Nauka/Interp eriodica".