G K White

Thermal expansion of solids at low temperatures

Abstract Studies of the thermal expansion of solids in the temperature range 1–100 K are reviewed. Effects due to thermal vibrations of the lattice, electrons, magnetic interactions and defects are fully discussed. The survey of experimental data is intended to be comprehensive. From the large volume of theoretical work in recent years the authors have aimed to select for discussion the most significant contributions.

Thermophysical properties of some key solids: An update

In 1985, the CODATA Bulletin published a Report of its Task Group on Thermophysical Properties of Solids which analyzed available data on, and gave recommended values for, the heat capacity of Cu, Fe, W, and Al2O3, the thermal expansion of Cu, Si, W, and Al2O3, the electrical resistivity of Cu, Fe, Pt, and W, the thermal conductivity of Al, Cu, Fe, and W, and the absolute thermopower of Pb, Cu, Pt, and W. The analysts for the different properties were R. B. Castanet, S. J. Collocott, P. D. Desai, C. Y. Ho, J. G. Hust, R. B. Roberts, C. A. Swenson, and G. K. White. The present paper is an updated version of the earlier report and includes more recent data which change some of the recommended values. notably the heat capacity of Cu and W and the thermal expansion of Si and W.

The low-temperature thermal expansion and Gruneisen parameters of some tetrahedrally bonded solids

The results of thermal expansion measurements using a three-terminal capacitance dilatometer on Ge, GaAs, ZnS, ZnSe and CdTe below 30K and on ZnSe and CdTe between 57 and 90K are reported. Respective values of 0.49, 0.32, -0.14, 0.0 and -0.85 derived for gamma 0th, the zero temperature limit of the Gruneisen parameter gamma =3 alpha VBs/Cp are given. These are in good agreement with the values of gamma 0el calculated from the pressure dependence of the elastic constants. gamma (T) as a function of reduced temperature, T/ theta 0, where theta 0 is the Debye temperature determined at the zero temperature limit, is found to have an essentially universal form and passes through a negative minimum at T approximately 0.06 theta 0. The implications of this observation and the importance of the degree of ionicity in dictating gamma 0 are discussed.

Thermal expansion of ZnTe and HgTe and heat capacity of HgTe at low temperatures

The linear coefficient of thermal expansion of ZnTe and HgTe is measured between 1.5 and 30K by means of a three-terminal capacitance dilatometer; the heat capacity of HgTe is measured in this temperature range. Values gamma 0th=0.07+or-0.07 (ZnTe) and -1.2+or-0.2 (HgTe) are obtained for the zero-temperature limit of the Gruneisen parameter. The former value is in good agreement with gamma 0el=0.05 calculated from the pressure derivatives of the elastic moduli. The low-temperature limiting value of the Debye temperature theta 0th=147.5+or-2K for HgTe. The variation of gamma (T) and theta D(T) as functions of reduced temperature, T/ theta D, fit the patterns established previously for other II-VI compounds of zincblende structure.

Thermal expansion of fluorites at high temperatures

The linear thermal expansions of CaF2, BaF2, SrF2, PbF2 and SrCl2 have been measured from room temperature up to their melting points. The linear coefficient alpha exhibits a Schottky-like bump similar to that observed previously for the heat capacity, Cp, and associated with fast-ion conduction in these fluorite-structure materials. Values for the Gruneisen parameter gamma (T) are included.

Thermal expansion of trigonal elements at low temperatures: As, Sb and Bi

Linear coefficients of thermal expansion have been measured from 2 to 30 K, 55 to 90 K, and at 283 K for single crystals of As, Sb and Bi inclined at various orientations to the symmetry axis. The principal coefficients alpha /sub /// and alpha perpendicular to and volume coefficient beta are reported, together with the Gruneisen parameters gamma , gamma /sub /// and gamma perpendicular to . The anisotropy of expansion is most marked for As and least for Bi: alpha is negative for As below about 150 K, for Sb below 20 K, but always positive for Bi. beta and hence gamma is positive for each: the limiting value is gamma 0=4.4+or-0.3 for As, 1.00+or-0.03 (Sb) and 1.9+or-0.1 (Bi). gamma (T) has a minimum at 8 to 10 K, a broad maximum between 20 and 40 K, and at room temperature approaches 1.5 for As and 1.0 for Sb and Bi.

Thermophysical Properties of Some Key Solids

In 1995 the Committee on Data for Science and Technology (CODATA) published a Report of its Task Group on Thermophysical Properties of Solids which analyzed available data on, and gave recommended values for, the heat capacity of Al2O3, Cu, W, and Fe, the thermal expansion of Cu. Si, W, and Al2O3, the electrical resistivity of Cu, Fe, W. and Pt, the thermal conductivity of AI, Cu, Fe, and W, and the absolute thermopower of Pb, Cu, and Pt, The Chairman of the Task Group was Professor Y. S. Touloukian. until his death in 1981, and later was Dr, Merrill Minges, Since that publication there have been more measurements of heat capacity (Cu), thermal expansion (Si and W), and thermopower (W). particularly at high temperatures with subsecond techniques, which have led us to reanalyze some of the data and change some “recommended” values, Revised tables and some algebraic expressions are presented here.

Thermal expansion of cuprous oxide at low temperatures

The linear thermal expansion coefficient alpha of cuprite (Cu2O) has been measured from 2 to 30K, 55 to 90K, and at room temperature; alpha is negative at low temperatures with a minimum value of -3*10-6 K-1 near 80K. The Gruneisen parameter has a limiting value of gamma 0=-4.5+or-0.2 at liquid helium temperatures, in fair agreement with the value of -4.0 calculated from elastic data.

Thermal properties of paratellurite (TeO2) at low temperatures

Measurements of the heat capacity, Cp, from 0.6 to 15 K can be represented by Cp=(0.32+or-0.02)T3 mJ mol-1 K-s ( theta D0=265+or-10 K) below 10 K. Linear thermal expansivities parallel ( alpha /sub ///) and perpendicular ( alpha perpendicular to ) to the symmetry axis from 2 to 120 K show marked anisotropy; alpha perpendicular to is negative below 10 K (while alpha /sub /// remains positive) but becomes positive and much larger than alpha /sub /// above 50 K. The Gruneisen parameter, gamma , increases from approximately=1 at 3 K to +1.4 at 30 K and is approximately=0.9 room temperature.

Thermal expansion and heat capacity of cuprous chloride at low temperatures

The linear thermal expansion of a polycrystalline sample has been measured in the ranges 1.5<T<34K, 55<T<90K, and at room temperature; and its heat capacity in the range 1.3<T<16K. Expansion is strongly negative at low temperatures, with Gruneisen parameters gamma 0th=-2.4+or-0.4 and gamma minth=-2.71; gamma infinity th=0.75+or-0.15. Debye temperatures are Theta 0C=179+or-0.6K, Theta minC=119K, Theta infinity C=285+or-10K. The elastic and piezoelectric measurements of Hanson et al. (1974) are used to calculate Theta el=182.2+or-2K, gamma el=-1.19+or-0.2. When CuCl is compared with other crystals of zincblende structure, gamma 0th and Theta infinity C/ Theta 0C correlate well with increasing ionicity, but no such trend is observed for the depth of the minima in gamma th(T) and Theta C(T).