Correlation between grain size and electrical properties of high‐temperature lead‐free 0.70BiFeO3‐0.30BaTiO3 ceramics

Abstract 0.70BiFeO 3 ‐0.30BaTiO 3 (0.70BF‐0.30BT) ceramics have been widely concerned because of their potential applications for high‐temperature piezoelectric devices. In this work, a series of dense 0.70BF‐0.30BT ceramics with average grain size variation from 0.55 to 6.0 μm were prepared. XRD results indicate that 0.70BF‐0.30BT ceramics show the coexistence of rhombohedral and pseudo‐cubic phases and the volume fraction of the rhombohedral phase increase with the grain size. The dielectric, ferroelectric and piezoelectric properties increase with the grain size initially from 0.55 to 5.0 μm and then decrease slightly. Values of d 33 , P r , and ε r, of 0.70BF‐0.30BT ceramics with the grain size of 5.0 μm are 185 pC/N, 21.2 μC/cm 2 , and 638, respectively, about five times higher than those ceramics with fine‐grain of 0.55 μm. Of particular importance is that 0.70BF‐0.30BT ceramics with large grain sizes possess better piezoelectric thermal stability due to the much stabler poled domain state with the rising temperature. The detailed structural studies indicate that the enhanced electric properties are owing to the significantly improved domain motion and the increased lattice distortion. This clarifying the relationship between electrical properties and grain size offers a novel way of improving the performances of piezoceramics.