Synthesis and dielectric properties of layer-structured compounds A(n-3)Bi(4)Ti(n)O(3n+3) (A = Ba, Sr, Ca) with n > 4

摘要

Several bismuth layer-structured compounds A(n-3)Bi(4)Ti(n)O(3n+3) (A = Ba, Sr, Ca) with n > 4 were synthesized and investigated. The average radius of A-site cations was found to be closely related to the lattice parameters in the a-b plane and, therefore, closely related to the stability of the layer structure. For Ba2Bi4T5O18 ceramics, there was a diffused phase transition centered at approximately 330 degrees C, which should be due to the cation redistribution of A-site Ba2+ and Bi3+ in the (Bi2O2)(2+) layer. For Sr2Bi4T5O18 ceramics, a sharp, dielectric constant peak was found at 325 degrees C. Ceramics of five-layered Ca2Bi4Ti5O18 and six-layered Ca3Bi4Ti6O21 showed temperature-stable dielectric constants up to 800 degrees C, and ferroelectricity was observed. In addition, as ferroelectrics, these Ca-containing bismuth layer-structured compounds showed frequency-independent dielectric constants > 150 and small tan delta on the order of 10(-3)-10(-4) in the frequency range of 1 kHz to I MHz.