CaTiO3 induced ferroelectric phase coexistence and low temperature dielectric relaxation in BaTiO3–BaZrO3 ceramics

The series of 0.86BaTiO3–(0.14−x)BaZrO3–xCaTiO3 (abbreviated as BT–BZ–xCT) ceramics with 0.03 ≤ x ≤ 0.11 were studied to obtain high piezoelectric properties. Rietveld refinement analysis indicated that the BT–BZ–CT compositions follow a gradual rhombohedral (R) → orthorhombic (O) + R → O + tetragonal (T) → T phase transformation with increasing x. Clear evidence of the series of ferroelectric phase transitions was also found in the dielectric results. The R-O and O-T transition temperature shifted close to ambient temperature, while the Curie temperature slightly increased with increasing x. In addition to the dielectric loss peaks associated with the structural phase transitions, a broad low-temperature dielectric loss peak was detected in the R phase at T = 90-150 K. This dielectric relaxation was attributed to the domain wall freezing and fits well to the Vogel-Fulcher model with activation energy Ea ≈ 60-300 meV and freezing temperature TVF ≈ 75-140 K. High piezoelectric strain coefficient (d33*) of about 1030 pm/V at 10 kV was achieved at x = 0.07, and a high Curie temperature (TC) was maintained at about 375 K.