Correlation Between the Microstructure and Electrical Properties in High-Performance (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead-Free Piezoelectric Ceramics

Using three different sintering methods: spark plasma sintering, two-step sintering, and normal sintering (Ba0.85Ca0.15)(Zr0.1Ti0.9)O-3 (BCZT) lead-free piezoelectric ceramics with grain sizes in the range of 0.43-2.2 mu m were prepared. The effects of grain size on the electrical properties and temperature stability of BCZT ceramics were systematically investigated. Results showed that reducing grain size shifted both the Tc and TT-R to higher temperatures, and tended to enhance the relaxor behavior. A strong dependence of piezoelectric properties on the grain size was observed, and similar to 10 mu m was a critical point for fabricating high-performance BCZT ceramics. For samples with grain sizes >10 mu m, excellent piezoelectric properties of k(p) > 0.48, (k)t > 0.46, d(33) > 470 pC/N and d(33)* > 950 pm/V were obtained. Moreover, no evident relationship between the grain size and temperature stability existed in this material, and all samples exhibited thermal instability below the Curie temperature. However, increasing grain size was helpful for improving the resistance to thermal depoling. The depolarization was assisted by internal mechanical stresses and the movement of 180 degrees and 90 degrees domain walls, which explained the increased resistance to thermal depoling in coarse-grained samples.