EN
Zn_{1-x}Be_{x}Se, Cd_{1-x}Mg_{x}Se and Zn_{1-x-y}Be_{x}Mg_{y}Se mixed crystals grown from the melt with different concentrations of Be and Mg have been characterized by photoluminescence and photoacoustic methods. An increase in band gap energy with increasing Be and Mg contents was observed. The photoacoustic spectroscopy was also employed for evaluation of thermal diffusivity of mixed Zn_{1-x}Be_{x}Se crystals with different beryllium contents.