Effects of oxide additives on structure and properties of bismuth ferrite-based ceramics

Effects of oxide additives (Bi 2 O 3 , MnO 2 , La 2 O 3 , Sm 2 O 3 , SnO 2 , and Nb 2 O 5 ) on structure and properties of 0.70Bi 1.05 FeO 3 –0.30BaTiO 3 ceramics were investigated. Their microstructure and electrical properties were dependent on the types and contents of oxide additives. A large piezoelectric constant ( d 33 ) of 135–200 pC/N together with a high Curie temperature of 454–504 °C can be obtained in the ceramics with R-C phase boundary. Most of oxide additives can induce the formation of saturated P–E loops and butterfly-shaped S–E curves, while a pinched P–E loop and sprout S-E curve were observed in the Nb 2 O 5 -modified ceramics due to a completely suppressed ɛ r – T curve and seriously refined grain sizes. There were high bipolar strain values ( S = 0.17%) under low driving electric fields for the addition of 0.5%mol Nb 2 O 5 . In addition, an enhanced magnetization of M r = 0.018 emu/g was achieved in the ceramics with 1.0% SnO 2 due to the structure distortion and the breaking of spin helix structure.