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 x < 0.5 a behavior similar to (NH4)(2)BEF4, while for x > 0.5 the behavior is more similar to (NH4)(2)(SO4), which is explained by the shortest ammonium-ion 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.