To improve the quality of CdZnTe (CZT) crystal, a thermal treatment was conducted by using Cd1-yZny alloy as an annealing source. Guided by our calculations of the correlations of the partial pressures between CZT crystal and Cd1-yZny alloy, optimized conditions for the gas-solid equilibrium annealing of CZT were experimentally studied. Characterizations revealed that the concentration distribution was uniform, and the defect density was decreased by more than one order of magnitude. The structural and electrical properties of the CZT crystal were evidently improved by this thermal annealing. (c) 2006 Published by Elsevier B.V.