The thermal decompositions of pure and mixed manganese carbonate and ammonium molybdate tetrahydrate in molar ratios of 3:1,
1:1 and1:3 were studied by DTA and TG techniques. The prepared mixed solid samples were calcined in air at 500, 750 or 1000C
and then investigated by means of an XRD technique. The results revealed that manganese carbonate decomposed in the range
300–1000C, within termediate formation of MnO2, Mn2O3 andMn3O4. Ammonium molybdate tetrahydrate first lost its water of crystallization on heating, and then decomposed, yielding water
and ammonia. At 340C,MoO3 was the final product, which melts at 790C. The thermal treatment of the mixed solids at 500, 750 or 1000C led to solid-solid
interactions between the produced oxides, with the formation of manganese molybdate. At 1000C, Mn2O3 and MoO3 were detected, due to the mutual stabilization effect of these oxides at this temperature.