Synthesis of calcium metastannate (CaSnO3) by solid state reactions in mechanically activated mixtures calcium citrate tetra hydrate [Ca3(C6H5O7)2·4H2O] – tin(II) oxalate (SnC2O4)

• The solid state reactions in the mixtures occur in three stages of mass loss.
• The mean dehydration enthalpy decreases in the milled mixture.
• The enthalpy of decomposition–combustion of the milled mixture is ≈−500 J/g higher.
• The peak of the last stage of the reaction is exothermic in the milled mixture.
• A 3 h-stage of annealing of the milled mixture at 850 °C yields pure CaSnO3.

Many synthesis procedures have been worked out to prepare CaSnO3. A great deal of them resort to the classical ceramic method that implies a very high temperature treatment (1300–1500 °C) of the component oxides mixture. To avoid such high temperature treatment, many alternative routes have been proposed. In this paper stoichiometric mixtures of Ca citrate tetrahydrate and Sn(II) oxalate have been mechanically activated by high energy milling. The reactions taking place in the mixtures during annealing have been studied by coupled TG–DSC measurements, XRPD and diffuse reflectance FT-IR spectroscopy. It has been established that the stage of mechanical activation allows the synthesis to be completed by 3 h-annealing at 850 °C.