Influences of Sintering Methods on Microstructure and Physical Property of (K,Na,Li)(Nb,Sb,Ta)O3 Piezoelectric Ceramics

(K,Na)NbO3-based ceramics (KNLNST ceramics) are a very promising type of lead-free piezoelectric materials. However, only limited studies were reported on them prepared by two-step sintering. Here, a comparison study was performed between two kinds of (K0.4425Na0.52Li0.0375)(Nb0.8825Sb0.08Ta0.0375)O-3 ceramics that were prepared by either conventional sintering (CS) or two-step sintering (TSS). It was found that TSS largely increases the relative density rho' and piezoelectric coefficient d(33) from 95.0% and 363 pC/N of CS to 97.0% and 387 pC/N, respectively. KNLNST ceramics prepared by two kinds of sintering methods show significant differences between microstructure and domain structure. The KNLNST-CS ceramic has small grain sizes but distributed uniformly, and their domain patterns in most grains are simply a group or groups of parallel stripes. In contrast, the KNLNST-CS ceramic has a non-uniform grain-size distribution, with many large grains displaying broad bands, and existing fine strips.