Study on the mixed crystals (NH4)2(BeF4)1-x(SO4)x

A study on the mixed crystals of formula (NH4)2(SO4)X(BeF4)1-x has been carried out, using thermal analyses, X-ray diffraction on powder and single-crystal samples at different temperatures. It is shown that these mixed crystals are isomorphs, showing for × 0.5 the behavior is more similar to (NH4)2SO4, which is explained by the shortest ammoniumion hydrogen bond lengths for the majority component. The presence of second ion produces a delay in the transition temperature. And it has been studied the inhomogenity of mixed crystal, which difficults obtain the compound discontinuity of two behaviors.