Thermodynamic Properties of ZnTe in the Temperature Range 15-925 K

Abstract

Subject classification: 65.40.Ba; S8.13The heat capacity of ZnTe was measured in an adiabatic calorimeter in the temperature range from 15 to 330 K and by DSC at T = 290-925 K. The following standard thermodynamic properties of ZnTe were derived: C 0 p (298.15 K) = (49.52 AE 0.10) J K --1 mol --1 ; S 0 (298.15 K) = (81.94 AE 0.17) J K --1 mol --1 ;H 0 (298.15 K) --H 0 (0 K) = (10.98 AE 0.02) kJ mol --1 ; F 0 (298.15 K) = (45.12 AE 0.10) J K --1 mol --1 . Temperature dependences of the heat capacity and the Gibbs free energy function are derived for the temperature range up to 1500 K. The Debye temperature calculated from the specific heat data is Q D = 252 K.An ever-growing interest in cadmium-and zinc-telluride based semiconductors is associated with the application of these materials in X-ray, g-and IR-radiation detectors. Because of the high melting point, high vapor pressure and non-stoichiometry, crystal growth of these materials is a rather complicated procedure [1]. Fundamental thermodynamic properties, in particular heat capacity and Gibbs free energy, are the basis for computer modeling of crystallization, post-growth cooling and annealing parameters.The heat capacity of ZnTe has been measured earlier only at low temperatures: Demidenko and Maltsev [2] reported adiabatic calorimeter measurements from 55 to 300 K, and Irwin and LaCombe [3] used an adiabatic calorimeter with (Au + 0.03% Fe) vs. chromel thermocouples for specific heat measurements in the temperature range from 15 to 150 K; the latter results can be considered only as semi-quantitative.In this paper we report heat capacity measurements of ZnTe in a wide temperature range, 15 to 925 K, including the first experimental results at high temperatures.Crystalline ZnTe was prepared from high purity elements produced by NORANDA Co., Canada. The total impurity content was less than 1 ppm. The synthesis was carried out in a pumped and sealed quartz ampoule with vibrational homogenization. According to the XRD analysis, the sample was single phase with a cubic structure. Vapor pressure measurements at T > 800 K confirmed that the sample was within the homogeneity range of ZnTe.The heat capacity of ZnTe was measured in an adiabatic calorimeter at temperatures 15-327 K and by DSC at T = 290-950 K. Experimental results (84 points) are pre-1

Unprecedented Integral-Free Debye Temperature Formulas: Sample Applications to Heat Capacities of ZnSe and ZnTe

“…Figure 3: Fitting of the set of low ( ) data (I) provided for ZnTe by Kremer et al [46] in combination with the upper section (102 K < < 327 K) of the low ( ) data set given by Gavrichev et al [38] (◻), a set of approximate high ( ) data points due to Gadzhiev et al [80] (◼) (which we have redigitalized from their Figure 1), and a series of equidistant (smoothed) high ( ) data points ( * ) available from the SGTE data review [81]. For comparisons with other data available for ZnTe we have also visualized the low-temperature data points given by Demidenko and Maltsev [31] (+) and Irwin and Lacombe [33] (◊), including the smoothed high-temperature data points quoted by Gavrichev et al [82] (◻) [ ( ) curve (-; see (5)) and ℎ ( ) curve (-----; see (4), in combination with (9) and (14) to (17)]. Figure 2) and for ZnTe (Figure 3), using (5) in combination with (9) and (14) to (17).…”

High Temperature Thermodynamic Properties of ZnTe(s)

“…The points shown from Gavrichev et al [16,17] are their extrapolation of measurements extending only to 983 K. Earlier equations by Mills [8] and by us [7] gave heat capacities of, respectively, 73 and 63.4 J/mol K at the melting point compared to the value of 60 from Eq 7.…”

“…At low temperatures the measured heat capacities from Irwin and LaCombe [23] covering 15-140 K and those from Demidenko and Mal'tsev [13] [16] calculate 81.94 for the same quantity. Mills [8] selected 77.82 ± 2/mol K based on the 56-300 K heat capacity available at that time and on emf measurements.…”

“…The heat capacity of ZnTe(s) from various sources [13][14][15][16][17][18] and for temperatures above 170 K is shown in Fig. 1.…”

“…The sample was a 2.1 mg crystal originally annealed in liquid Zn at 1043 K. Correspondingly the vapor is initially Zn rich but with increasing temperature the ratio approaches and then holds at a value of 2. As pointed out in Ref Demidenko and Mal'tsev, [13] Malkova et al, [14] Pashinkin et al, [15] Gavrichev et al, [16,17] Yamaguchi. [18] The solid curve is the fit to these data given by Eq 7 in the text.…”