The spark plasma sintering (SPS) method was applied to prepare dense compacts of proton conducting Sr-doped LaPO4 at relatively low sintering temperatures. A relative density higher than 98% could be achieved with the SPS method when sintering temperatures above 1323 K were employed, whereas no more than 94% was achieved with the conventional pressureless sintering ∼ PLS! method at 1473- 1573 K. Mechanical properties, e. g., three- point bending strength and Vickers hardness, of the SPS samples were considerably improved compared with those of the PLS samples. The SPS samples prepared at 1323- 1373 K exhibited a bending strength of 240 MPa and a Vickers hardness of 6.7 GPa. However, higher SPS temperatures than 1373 K diminished the mechanical properties probably because of the grain growth with increased sintering temperature. Conductivity measurements under various psH2Od and psO2d conditions showed that the Sr- doped LaPO4 sintered with the SPS method exhibited dominant protonic conduction regardless of the sintering conditions and that the conductivities were comparable with those of the PLS samples. Throughout this work, the SPS method was demonstrated as an effective tool to prepare proton conducting phosphatebased ceramics with a high density and excellent mechanical properties while maintaining the feature of protonic conduction. © 2005 The Electrochemical Society. All rights reserved.