Preparation of Proton Conducting Sr-Doped LaPO₄ Ceramics with the Spark Plasma Sintering Method

The spark plasma sintering (SPS) method was employed to prepare sintered specimens of proton conducting Sr-doped LaPO₄ ceramics. The relative densities of the sintered Sr-doped LaPO₄ were around 99% when higher sintering temperatures than 1050°C were applied for the SPS process, while only 93% of relative density was achieved with the conventional pressure-less sintering (PLS) method at 1200°C. Electrical conduction properties of the sintered samples with the SPS method at 1200°C were evaluated by using conductivity measurements at 500-930°C under 0.4-5 kPa of p(H₂O) or p(D₂O) and 0.01-100 kPa of p(O₂). The specimen prepared with the SPS method showed similar conductivities and conduction properties as that prepared with the PLS method. These results suggested that the SPS method was a useful sintering technique to prepare proton conducting phosphate-based ceramics with a high density while keeping a feature of protonic conduction.