Thermodynamic calculations and modeling of the hydrothermal synthesis of nickel tungstates

A thermodynamic model of electrolytic solutions was applied to determine the reaction conditions favoring the hydrothermal synthesis of nickel tungstate, an antiferroelectric material commonly used for catalysts and humidity sensors. Yield diagrams were constructed relating the equilibrium concentration of the chemical species as a function of temperature, pH and reagent concentration. The theoretical predictions were corroborated by experiments and we were thus able to avoid the empirical “trial-and-error” mode of synthesis.