We developed a hydrothermal synthesis method for lead-free perovskite (Bi1/2K1/2)(ZrxTi(1-x))O-3 (BKZT) powders. Singlephase BKZT powders with various nominal Zr contents as high as x = 0.10 were obtained using amorphous hydrous oxide (ZrxTi1-x)O-2 center dot nH(2)O precursors prepared by the hydrolysis of Zr- and Ti-alkoxides, whereas a reaction using a mixture of crystalline TiO2 and ZrO2 powders did not provide single-phase BKZT. Elemental analysis revealed that the Zr contents of the obtained BKZT powders were slightly higher than the nominal values. The powders had fine particle sizes smaller than 300 nm and were stable against a high-temperature heat treatment at 1000 degrees C. These observations suggest that the hydrothermally derived powders are suitable for use in fabricating bulk BKZT ceramics via sintering. (C) 2017 The Ceramic Society of Japan. All rights reserved.