VALIDITY OF THE LATTICE-PARAMETER VEGARD-RULE IN CD1-XZNXTE SOLID-SOLUTIONS

Cd1-xZnxTe crystals of different composition (0 less than or equal to x less than or equal to 1) were grown by the vertical Bridgman method and by synthesis in Te excess. After careful surface preparation of cr ystal slices, their Zn:Cd ratios were ascertained by wavelength-disper sive X-ray spectroscopy (WDXS), and the lattice parameters of the same slice regions were measured by X-ray diffractometry. The Vegard rule concerning the linear lattice-parameter dependence on composition is - in contrast with earlier literature data - exactly valid within the l imits of error (Delta x less than or equal to +/-0.01 and Delta a/a le ss than or equal to 3.7 . 10(-4)) and follows the equation a(x) = (0.6 4822 - 0.03792x) nm. After annealing some slices at different temperat ures and controlled partial pressure conditions in order to find possi ble phase separations or cation ordering effects, neither the lattice parameters were changed nor additonal interferences were found. ii pub lished occurrence of a rhombohedral phase could not be confirmed by me ans of powder diffraction analysis. The results are discussed in relat ion to own electron diffraction investigations and to EXAFS literature data.