Fabrication of Al2O3-coated BiFeO3 particles and fine-grained ceramics with improved electric properties

Abstract

(1-x)BiFeO3@xAl2O3 ceramics with x = 0, 2.5, 5, and 7.5 mol% were prepared via the Stöber coating method. The effects of Al2O3 coating on microstructure, dielectric, and ferroelectric properties had been investigated. At x = 5 and 7.5, the samples had a great Al2O3 coating effect. XRD results indicated that excessive Al2O3 coating increased the formation of secondary phases (Bi2Fe4O9 and Bi24A12O39). After the coating of Al2O3, the samples had higher relative density and decreased loss tangent. Compared with the pure BiFeO3 sample, the Al2O3-coated samples had improved Bi-O strength, less oxygen vacancy, and the reduction of Fe3+ was decreased. The leakage current density decreased gradually. At x = 5, the sample had the highest Pr value (1.53 μC/cm2). These electric properties changes were ascribed to the generation of secondary phases, the ne grains, and the fewer vacancies.