This experimental study reports the mechanical energy harvesting from piezoelectric single crystal materials with operating range higher than 500 ��C and compares their performance with state-of-the-art soft Pb(Zr,Ti)O 3 (PZT) material. Yttrium calcium oxyborate YCa4O(BO 3)3 (YCOB) and lanthanum gallium silicate La 3Ga5SiO14 (LGS) crystals were found to exhibit stable piezoelectric and dielectric properties up to 1000 ��C. Single and three-crystal stacks of YCOB, LGS, lithium niobate LiNbO3 (LN), and soft PZT were tested in longitudinal mode configuration (33-mode). The power density of soft PZT was found to be about three orders of magnitude higher than that of high temperature crystals at room temperature however its operating range was limited to 150 ��C. On the other hand, YCOB and LGS crystals annealed at 600 ��C exhibited similar magnitude of power as that at room temperature. �� 2009 The Japan Society of Applied Physics.