Relaxor Behavior and Large Room-Temperature Polarization of Ferroelectric Sr4CaBiTi3Nb7O30 Ceramics

A new relaxor ferroelectric ceramics, Sr4CaBiTi3Nb7O30, were prepared. The microstructure, morphology, dielectric, and ferroelectric properties were studied. The ceramics were found that growing in some directions preferentially. Two dielectric relaxations were observed below the Burns temperature T-B=460K and relaxation-I can be described by the Vogel-Fulcher law. The Curie-Weiss constant (C) of 1.33x10(5)K confirms the displacive-type ferroelectric phase transition. The ceramics exhibit the first-order diffuse ferroelectric phase transition feature. The diffusion exponent varies from 1.99 to 1.92 with different applied frequencies. Room-temperature (RT) polarization was evaluated, and P-r= 2.6C/cm(2,)E(c)=15.2kV/cm values were obtained. The high breakdown voltage (80kV/cm) and low leakage current confirmed the high quality of Sr4CaBiTi3Nb7O30 ceramics. All of these features suggest that Sr4CaBiTi3Nb7O30 may be used to substitute lead-based relaxor ferroelectric materials for environmental friendly. Raman spectra and polarization measured at different temperatures attribute the high- and low-temperature dielectric relaxation to flipping and breathing of polar nanoregions, respectively.