Composition and properties of layered compounds in the GeTe-Sb2Te3 system

The 620-K section of the Ge-Sb-Te phase diagram was mapped out using x-ray diffraction, microstructural analysis, and microhardness measurements. The transport properties of the layered tetradymite-like compounds nGeTe . mSb( 2)Te(3) (n, m = 1-4) were studied in wide temperature ranges (Hall effect a nd electrical resistivity, from 77 to 800 K, and thermoelectric power, from 90 to 450 K). The results show that the nGeTe . mSb(2)Te(3) compounds are degenerate p-type semiconductors with a fairly high hole concentration due to the high density of intrinsic point defects. The temperature dependences of the Hall coefficient and resistivity exhibit anomalies related to solid -state phase transitions. The room-temperature lattice thermal conductivity of nGeTe . mSb(2)Te(3) is fairly low, in the range 8-10 mW/(cm K).