MASS-SPECTROMETRIC STUDY OF VAPORIZATION AND THERMODYNAMIC PROPERTIES OF LI2ZRO3(S)

Partial pressures of Li(g), LiO(g), Li2O(g) and O2(g) over Li2ZrO3(s) have been determined by a mass-spectrometric Knudsen effusion method. Over various lithium-containing oxides, the partial pressures of Li2O(g) decrease in the following order: Li2O > Li5AlO4 congruent-to Li4TiO4 congruent-to Li8PbO6 > Li2SnO3 > Li4SiO4 > Li2TiO3 congruent-to Li2ZrO3 > LiAlO2 congruent-to Li2SiO3 > LiNbO3. From the gas-solid equilibria, enthalpies of formation for Li2ZrO3(S) from elements and from constituent oxides have been calculated to be DELTA(f)H298-degrees(Li2ZrO3,s) = -(1742.3+/-8.8) kJ mol-1 and DELTA(fox)H298-degrees(Li2ZrO3,s) = -(46.1+/-92) kJ mol-1, respectively. Enthalpies of the reaction for adding 1 mole of Li2O(s) to various oxides decrease with increasing the Li2O molar content. The results show that the oxides with less Li2O molar content have more ability to stabilize the pseudo-Li2O component for lithium aluminates, silicates, titanates, molybdates, ferrates and zirconates.