The heat capacity of cadmium telluride at medium and high temperatures

Abstract

The modified Schomeit method for processing enthalpies is suggested, which provides for agreement between high-temperature data on C p both with a reliably measured value of and with derivative . The latter gives a "smoother" joining of dependences C p (T) obtained experimentally with different accuracy. The suggested procedure is applied to analysis of experimentally obtained distributions of heat capacity of cadmium telluride as a function of temperature, and a new approximating equation is obtained for the most reliable data in the range from 298 K to the melting point of CdTe. This procedure is compared to other known methods of simultaneous processing of C p (T) data. It is demonstrated that the values of heat capacity of CdTe recommended by us agree with reliably determined coefficients of thermal expansion (CTE) of this compound. The characteristic Debye temperature of cadmium telluride is estimated in a wide temperature range, and the pattern of its variation with temperature is analyzed.

Mechanical and Thermal Properties

“…The latter relation is in better agreement with density values reported for HgTe [4] and CdTe [5][6][7][8] included in Figure 8.1, and can be used when the material stoichiometry is unknown. For metal-saturated samples an increment of up to 0.01 g cm −3 needs to be added, and a similar amount subtracted for tellurium-saturated material.…”

High Temperature Thermodynamic Data for CdTe(c)

“…and by Pavlova et al [3] give close to the same fits to the data used here we use a heat capacity that is the average of these two:…”

“…As mentioned earlier, this is because they used a heat capacity for CdTe that is about 16 J/mol K greater near 1365 K than that adopted here. Our earlier [6] analysis of the thermodynamic and phase diagram data for CdTe also used a heat capacity based upon the measurements of Mezaki et al, [8] which have been judged to be too large by Pavlova et al [3] …”

“…Recently, high temperature heat capacity determinations for CdTe(c) by Malkova et al [1] and by Yamaguchi et al [2] and by others at lower temperatures have been reviewed by Pavlova et al [3] Here we wish to extend this study of the thermodynamic properties of CdTe(c) to include experimental values for the high temperature Gibbs energy of formation. The standard enthalpy and entropy of formation at 298.15 are also required, but both are fairly well established.…”

“…[5,6] depended in part on an estimate of the heat capacity of CdTe(c) made by Mills. [7] which was based on the heat content measurements by Mezaki et al [8] According to Pavlova et al, [3] this heat capacity is high by as much as 15 J/mol K at the 1365 K melting point. Besides, assessments of the entire system are more complicated than necessary to establish the thermodynamic properties of the CdTe(c) phase itself.…”