X-ray phase analysis (XRD), differential thermal analysis (DTA) and IR spectroscopy have shown that continuous substitution
solid solutionsin are formed in the FeVMoO7–CrVMoO7 system. With increasing the degree of Cr3+ ion incorporation into the FeVMoO7 structure, a crystal lattice contraction of the Fe1–xCrxVMoO7 solid solution arise. Elevation of temperature of its incongruent melting and gradual shifting of the corresponding IR absorption
bands towards higher wavenumbers have been noticed, as well. The solid product of incongruent melting for x≤0.5 is the Fe4–yCryV2 Mo3 O20 solid solutions phase, whereas for x>0.5 Fe2–zCrz(MoO4)3 and Fe2–u Cru O3 solid solutions.