Grain size effects and structure origin in high-performance BaTiO3-based piezoceramics with large grains

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Grain size shows significant influence on electrical properties of piezoceramics. However, there are few works to investigate the grain size effects in high-performance and large-grain piezoceramics and uncover the structure origin. In this work, large grain size from ~53 to ~92 µm was achieved in a high-performance BaTiO3 (BT)-based ceramic via tuning sintering conditions. With grain size increasing, the ceramics exhibit same multiphase coexistence state, similar phase transition temperature, upward TC dielectric peaks and reduced diffuseness degree. Because of the larger and more complex non-180° domains within bigger grains, the improvement in remnant polarization (Pr), coercive field and negative strain were observed in bigger-grain ceramics. The elevated Pr finally leads to the piezoelectric coefficient d33 increasing from 500 to 650 pC/N. However, too large grains may cause the reduced strain due to the high remnant strain in first cycle. Therefore, big grain size is conducive to achieve high piezoelectricity while moderate grain size can facilitate strain response in high-performance ceramics with large grains, which is quite different with pure BT ceramic. This work presents insights into the grain size effects and affords guides to further optimize electrical properties in high-performance piezoceramics with large grains.