The field of thermoelectric energy conversion is reviewed from both a theoretical and an experimental standpoint. The basic theory is introduced and the thermodynamic and solid state views are compared. An overview of the development of thermoelectric materials is presented with particular emphasis being placed on the most recent developments in high-temperature semiconductors. A number of possible device applications are discussed and the successful use and suitability of these devices for space power is manifest.

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A high-temperature (1900 K) Seebeck coefficient apparatus is described in which small thermal gradients are generated in a sample by light pulses transmitted via light pipes. By employing an analog subtraction circuit, the Seebeck coefficient is displayed directly on an X–Y recorder. This technique presents a convenient, accurate, and rapid method for measuring the Seebeck coefficient in highly doped semiconductors as a function of temperature. The nature of the resulting display (X–Y recording) is a valuable tool in determining validity of the data. A straight line results (i.e., a minimum of hysteresis) only if all potential experimental errors are minimized. Under these conditions, the error of measurements of the Seebeck coefficient is estimated to be less than ±1%.

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The integral method of measuring the Seebeck voltage V(T), in which one end of the sample is held at a fixed temperature TC, and the other end is varied through the temperature T range of interest, has been adapted to short rod-shaped samples. The Seebeck coefficient S is obtained from the slope of the V(T) vs T curve, i.e., S=dV(T)/dT. The apparatus has been completely automated such that the specimen is automatically cycled through a preselected temperature range, up to a maximum temperature of 1000 °C, and the V(T), T, and TC values are acquired, stored, and analyzed by means of a microcomputer. Simplicity of sample handling and minimal operator involvement make this method well suited to the survey of large numbers of samples.