Special aspects of solid-phase synthesis of NiSiO and solid solution NiZnSiO with olivine structure

A study of the sequence of phase transformations of a mixture of simple zinc, nickel and silicon oxides during isochronous annealing in the temperature range of 800–1500°C was carried out in air using the X-ray phase analysis method. The main features of the mechanism of solid-phase synthesis of NiSiO and NiZnSiO were identified based on the obtained data. It has been shown that in the temperature range of 1300–1500°C, during the synthesis of NiSiO, the processes of structure formation of the cristobalite and olivine phases occur simultaneously; obtaining single-phase NiSiO requires hundreds of hours of annealing. Kinetic analysis of the phase formation sequence of NiZnSiO (x = 0.10, 0.25) showed that at 800°C a substitution solid solution of NiZnO is formed. As the temperature increases, the reaction mixture undergoes the sequential formation of solid solutions with the structure of willemite ZnNiSiO and olivine NiZnSiO. Annealing above 1200°C leads to the interaction of these solid solutions and the formation of NiZnSiO with a given elemental composition, and the time and temperature of the final annealing decrease with an increase of the zinc concentration x.