Combustion Synthesis of Nanometric Powders of LaPO₄ and Sr-Substituted LaPO₄

La (1 - x ) Sr ( x ) PO 4 materials are very stable at high temperature and water vapor partial pressure and they show protonic conductivity; thus, they could be used as electrolytes in HTPFCs (high-temperature protonic fuel cells), hydrogen sensors, and hydrogen separation technology. This work describes the combustion synthesis of La (1 - x ) Sr ( x ) PO 4 powders ( x = 0, 0.025, 0.050) from mixtures of La(NO 3 ) 3 ·6H 2 O and Sr(NO 3 ) 2 as cation precursors, (NH 4 ) 2 HPO 4 as anion precursor, and urea as fuel. The characterization of the as-prepared combustion products showed that combustion synthesis provides a straightforward method for the achievement of solid solutions of these materials as nanometric powders. Furthermore, dilatometric studies reveal that dense ceramics can be obtained at low sintering temperature (1300 °C), in air, from the synthesized nanometric powders.