Abstract <p>The phase transformation sequence in a mixture of zinc, nickel, and silicon binary oxides during isochronous annealing in the temperature range 800–1500°C was studied in air using X-ray powder diffraction. The gained data served to elucidate the main features of Ni₂SiO₄ and Ni_{2 – 2<i>x</i>}Zn_2<i>x</i>SiO₄ solid-phase syntheses. In the range 1300–1500°C, cristobalite and olivine structures are formed simultaneously during the Ni₂SiO₄ synthesis; hundreds of hours of annealing are required for single-phase Ni₂SiO₄ to be formed. The kinetic analysis of the Ni_{2 – 2<i>x</i>}Zn_2<i>x</i>SiO₄ (<i>x</i> = 0.10 or 0.25) phase formation sequence showed that a Ni_{1 –} _<i>x</i>Zn_<i>x</i>O substitutional solid solution was formed at 800°C. As the temperature increased, the reaction mixture underwent the sequential formation of willemite Zn_{2 – 2<i>x</i>}Ni_2<i>x</i>SiO₄ and olivine Ni_{2 – 2<i>x</i>}Zn_2<i>x</i>SiO₄ solid solutions. At annealing temperatures above 1200°C, these solid solutions reacted to yield Ni_{2 – 2<i>x</i>}Zn_2<i>x</i>SiO₄ with the tailored elemental composition; the time and temperature of the final annealing decreased as the zinc concentration <i>x</i> increased.</p>