Standard Enthalpy of Formation of Lanthanum Zirconate

The enthalpy of formation of lanthanum zirconate, La 2 Zr 2 O 7 , which is shown to have a distorted pyrochlore structure, was determined. High‐temperature solution calorimetry in molten lead borate was used to determine the heat of formation from the constituent oxides as −135.8 ± 6.4 kJ/mol at 974 K. Using additional data on the enthalpies of formation of the oxides and heat contents, this value was converted to a standard enthalpy of formation from the elements: Δ f H° 298.15 =−4130.4 ± 6.8 kJ/mol.