PREFACEThis monograph deals with the semiconducting compounds formed from elements of groups II, IV, or V and sulfur, selenium, or tellurium. These compounds are attracting increasing attention because they have interesting physical properties. The monograph describes the crystal structures of these compounds, and presents the published data on their polymorphic transitions, including transitions observed at high pressures. The problems of chemical binding are discussed.In the sections dealing with the phase diagrams, special attention is paid to the departures of semiconducting compounds from stoichiometry and investigation methods are described for the precise determination of the composition of these compounds. Analysis of the published material has shown that the characteristic feature of semiconducting compounds with a predominantly covalent type of chemical binding is a departure from stoichiometry. This departure is sometimes very small, representing hundredths and thousandths of 1%, but it strongly affects the physical properties of these compounds.The composition of these compounds does not remain constant, but is affected by external conditions: temperature, pressure, and the concentration of the third component. Because of this, the phase diagrams of the "temperature-composition" type are insufficient for many of these systems. It is also necessary to know the equilibrium phase diagrams of the "pressure-temperature-composition" (P-T-X) type. Knowledge of the P-T-X diagrams is particularly important in the synthesis of semiconducting compounds having high vapor pressures. The monograph includes all the published P-·T-X diagrams for the compounds discussed and describes a method for plotting these diagrams. Inves-V vi PREFACE tigations of the P-T-X diagrams of semiconducting compounds are of relatively recent origin and it is hoped that the review of these investigations will attract more attention of research workers to such diagrams. The more important physicochemical properties of the compounds are also given in the monograph. Unfortunately, the published material is insufficient for a full description of the thermodynamic properties of many of the compounds considered. More work should be done on these properlies.The main physical properties of the compounds are given: the forbidden band width, the carrier mobility, the effective masses of carriers, the electrical conductivity, and the thermoelectric power.The monograph consists of three chapters. The first deals with chalcogenides of elements in group II: zinc, cadmium, and mercury. The second discusses semiconducting compounds of elements in group IV: germanium, tin, and lead. These compounds are used in some photoelectric and thermoelectric devices. And the third describes investigations of compounds of elements of group V: arsenic, antimony, and bismuth. Allthese chalcogenides, as well as solid solutions based on them, are of great importance because of their application as thermoelectric materials in lowtemperature thermoelectric converters and ...
