Thermal analysis and mechanism of α-Zn2SiO4:Mn2+ formation from zinc oxalate dihydrate under hydrothermal conditions

► Dehydration and reaction of zinc oxalate dihydrate in high-temperature water were investigated. ► The dehydration became suppressed as the temperature and pressure increased. ► The suppression of dehydration greatly inhibited side reactions in α-Zn2SiO4 crystallization. ► Zinc oxalate dihydrate led to a high formation rate of α-Zn2SiO4 crystallization in high-temperature water.