Microstructure and Electrical Properties of Mn-doped Bismuth Layer-structured Bi₇Ti_4.5W_0.5O₂₁ Ceramics

Bi₇Ti_4.5-xMn_xW_0.5O₂₁ (BTW-BIT-x Mn) bismuth layered-structure ceramics were synthesized by using the traditional solid-state method. Structure and electrical properties of the Bi₇Ti_4.5-xMn_xW_0.5O₂₁were systematically studied. XRD and SEM results showed that all the samples were single phase bismuth layered compound and the grain growth was inhibited due to the doping with Mn. Electrical properties of the ceramics were improved after doping with Mn and the Bi₇Ti_4.45Mn_0.05W_0.05O₂₁ sample exhibited optimal properties, with a piezoelectric constant d₃₃ of 19.3 pC/N, Curie temperature of 701 ℃ and DC resistivity of 2.1×10⁸ Ω cm at 500 ℃. The annealing data indicated that more than 80% of the initial value of piezoelectric constant was retained at 550 ℃, demonstrating that the material has high thermal stability. Such BTW-BIT-x Mn ceramics have great potential for high-temperature piezoelectric applications.