Oxygen Vacancies and Electrical Properties in Cr substituted Bi4Ti3−xCrxO12 (x = 0, 0.01, 0.02, 0.03, 0.04) ceramics

Abstract

Numerous literatures have reported that the oxygen vacancy concentration of Cr-modified BiT ceramics will increase due to the acceptor effect of Cr replacing Ti at B-position. In this paper, a series of BiT ceramics doped with various Cr content were prepared by traditional solid phase method, we found trace amount of Cr doping preferences to enter the A-site of BiT ceramics and reduces the oxygen vacancy concentration while improving the piezoelectric properties and Curie temperature of BiT ceramics. The conduction mechanism for all Bi₄Ti_3−xCr_xO₁₂ (x = 0, 0.01, 0.02, 0.03, 0.04) ceramics are mainly contributed by the contribution of single ionizing oxygen and the jump of partial double ionizing oxygen. Raman measurements reveal that the dopant of Cr³⁺ in BiT ceramics can enter the A and B sites in the oxygen octahedron and the Bi-site in bismuth layers simultaneously, a small amount of Cr³⁺ doping will preferentially enter the A-site and the Cr³⁺ doping amount over 0.01 will gradually also enter the B-site, where the BiTC-2 and BiTC-3 ceramic samples present more significant shifts at the modes in A-site after Cr doping. Furthermore, Bi₄Ti_2.98Cr_0.02O₁₂ ceramics maintains the highest piezoelectric constant of d₃₃ = 21 pC/N and the highest Curie temperature of T_C = 702 °C.