Magnesium orthostannate Mg2SnO4 can be synthesized at 900-degrees-C with high purity using the peroxide route. The powder shows large specific surface area and small grain size, leading to high sinterability. A peroxo-precursor is formed during the synthesis by a precipitation step from aqueous solution. The thermal decomposition of the X-ray amorphous precursor leads directly to Mg2SnO4. Magnesium metastannate MgSnO3 is formed after thermal degradation of a corresponding peroxo-precursor at temperatures below 700-degrees-C. Further thermal treatment at temperatures above 700-degrees-C leads to the decomposition of MgSnO3 to Mg2SnO4 and SnO2.