Preparation of CuO-doped (K,Na,Li)(Nb,Ta)O3 ceramics with a homogeneous microstructure by Two-step sintering for multilayered piezoelectric energy harvesters

Abstract A two-step sintering method for the fabrication of homogeneous microstructures in CuO-doped [(K 0.485 Na 0.515 ) 0.935 Li 0.065 ](Nb 0.99 Ta 0.01 )O 3 (KNLNT) ceramics without abnormal grain growth is studied. The CuO-doped KNLNT ceramics prepared by normal sintering at temperatures greater than 900 °C resulted in inhomogeneous microstructures with a bimodal grain size distribution. In contrast, two-step sintering (920–930 °C for 0 h in the first step and 880 °C for 1–12 h in the second step) resulted in a homogeneous microstructure with a grain size of a few micro-meters. The samples prepared by two-step sintering had superior piezoelectric properties and piezoelectric energy harvester (PEH) figure of merit comparable to samples prepared by normal sintering. Multi-layered PEH with CuO-doped KNLNT ceramic layers with homogeneous microstructures were successfully fabricated by a two-step sintering method and their harvesting characteristics were measured.