The vertical Bridgman＇s method was employed to prepare a single crystal of the (2GaAs)(0.5) (ZnSiAs2)(0.5) system. The X-ray Laue method examination shows that the ingot prepared is a single crystal 2 cm long and 0.9 cm in diameter. The EPMA, AES, and ESCA analysis shows that the specimen was uniform and the composition stoichiometry is within the experimental error limit. The room temperature and temperature dependence X-ray powder diffraction were carried out to determine the lattice parameter, X-ray density and thermal expansion coefficient over temperature range 20 degrees C-772 degrees C.