Lead-free rare earth-modified BiFeO3 ceramics: Phase structure and electrical properties

Abstract

Here we investigated the phase evolutions as well as the relationships between phase structure and electrical properties of BFO ceramics by doping rare earth elements (i.e., Eu, Pr, Sm, La, Dy) with different concentrations. It was found that the phase structure of the ceramics was strongly dependent on the types and concentrations of rare earth elements: rhombohedral phase for Eu, Pr and La with x≤0.10, Dy with x≤0.15, Sm with x≤0.075; orthorhombic for Eu with 0.15<x≤0.30, and Sm and Dy with 0.20<x≤0.30; triclinic phase for Pr with 0.20<x≤0.30, and La with 0.10<x≤0.20; monoclinic for La with 0.20<x≤0.30; rhombohedral-orthorhombic for Eu with 0.10<x≤0.15, Pr with 0.10<x≤0.20, and Dy with 0.15<x≤0.20. Interestingly, the ceramics with rhombohedral phase always exhibited better piezoelectric and ferroelectric properties with respect to the ones with multiphase coexistence or other phases. In addition, both high piezoelectric constant (d33>40 pC/N) and low dielectric loss (tan δ≤0.01) can be achieved in the ceramics with rare earth elements (Eu, Pr, Sm, La).