A-site substitution effect of strontium on bismuth layered CaBi4Ti4O15 ceramics on electrical and piezoelectric properties

Strontium substituted CaBi4Ti4O15 ceramics with the chemical formula Ca1−xSrxBi4Ti4O15 (CSBT) (x = 0.0-1.0) have been prepared through conventional solid state route. The formation of single phase material with orthorhombic structure was verified from X-ray diffraction with incorporation of Sr substitution. Decrease in a-axis displacement of Bi ion in the perovskite structure in the CSBT ceramics were observed from the relative changes in soft mode (20 cm−1) in the Raman spectra, and increase in Sr incorporation shows the shift in ferroelectric to paraelectric phase transition temperature. The dielectric properties for all the CSBT ceramic compositions are studied as a function of temperature over the frequency range of 100 Hz-1 MHz. Curie's temperature was found to be function of Sr substitution and with increase in the Sr concentration the phase transition becomes sharper and phase transition temperature gets shifted towards lower temperature (790-545 °C). The behavior of ac conductivity as a function of frequency (100 Hz-1 MHz) at low temperature (<500 °C) follows the power law and attributed to hopping conduction mechanism. Sr substitution results in the increase in piezoelectric coefficients (d33) whereas piezoelectric charge coefficient values were found comparable to that of PZT at room temperature. Relative changes in soft modes due to Sr incorporation results in high piezoelectricity in the CSBT ceramics.