Boosting energy harvesting performance in (Ba,Ca) (Ti,Zr)O3 lead-free perovskites through artificial control of intermediate grain size

In this study, (Ba0.85Ca0.15)(Ti0.9Zr0.1)O-3 (BCTZ) lead-free ceramics with enhanced energy density were prepared by two-step sintering. All ceramics fall into the rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary near room temperature, and a dense microstructure with an intermediate grain size was observed. The enhanced piezoelectric and energy harvesting properties were attained over a wide grain size range of 10-15 mu m, benefiting from the construction of the R-O-T phase boundary. Most interestingly, the maximum values of d(33) and d(33) x g(33) (530 pC N-1 and 9720 x 10(-15) m(2) N-1) can be achieved at 1500/1350 degrees C with a grain size of 13.7 mu m. The interpretation of the underlying mechanism related to domain and defect engineering has been investigated systematically. Furthermore, a high output power of 99 mu W and an energy conversion efficiency of 10% were obtained at a simple cantilever energy harvester fabricated from a 1500/1350 degrees C specimen under an acceleration of 1.0g, making the current system very promising for piezoelectric energy harvesting applications.