1. X-ray study of thermal expansion behaviors and Grüneisen parameters of cadmium germanium arsenide crystal over the temperature range 25-450 °C.
- Author
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Liu, W., Zhao, B., Zhu, S., He, Z., Chen, B., Huang, W., Tang, J., and Yu, Y.
- Subjects
X-ray diffraction ,CHALCOPYRITE ,THERMAL expansion ,ANISOTROPY ,CADMIUM - Abstract
X-ray diffraction measurements of tetragonal chalcopyrite cadmium germanium arsenide crystal are carried out over the range 25-450 °C. The collected patterns show that the powder neither yields a new phase nor structurally transforms to any other architecture. Accurate lattice parameters (including two lattice constants a and c, cell volume V, axial ratio k, and tetragonal distortion δ) are determined by means of Cohen's least square method. Polynomial fit approximation is adopted to quantitatively describe the temperature dependence of lattice parameters. These results are the groundwork that allows the evaluation of thermal expansion coefficients defined as αR = R-1(dR/dT) where R represents lattice parameters. The average thermal expansion coefficients are evaluated, 13.9 × 10-6 K-1 for αa and 2.8 × 10-6 K-1 for αc, respectively. It is also found that αa increases while αc decreases with temperature, which in consequence brings forth the large anisotropy of thermal expansion between the two main axes (a-axis and c-axis). Detailed discussion reveals that the anisotropy behavior is in tight association with the nearest neighboring bonds. Namely, the thermal expansion coefficient perpendicular to c-axis (αa) depends to a large extent on the ionic Cd-As bonds, while that parallel to c-axis (αc) depends on the covalent Ge-As bonds. Finally, the Grüneisen parameters at different temperatures are evaluated and also exhibit anisotropic behavior (γa > γc). It is found that γa is temperature-dependent and increases with temperature, while γc tends to be temperature-independent. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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