Phase evolution and enhanced electrical properties of (Ba_0.85Ca_0.15−x Y _x )(Zr_0.1Ti_0.9)O₃ lead-free ceramics

(Ba_0.85Ca_0.15−x Y _x )(Zr_0.1Ti_0.9)O₃ (x = 0.00, 0.01, 0.02, 0.03 and 0.04) lead-free ceramics with excellent performance were fabricated using a solid-state reaction method. The effects of Y₂O₃ substitution on the crystal structure and electrical properties were investigated in detail. On the basis of the X-ray diffraction, it was clear that Y₂O₃ additive induced phase transition from orthorhombic phase to the coexistence of orthorhombic and tetragonal phases, and then to single tetragonal phase at room temperature with increasing x. Dielectric measurements revealed that a gradual change presented from typical ferroelectric behavior in (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ to dispersive relaxor-like characteristics in substituted samples. In addition, double permittivity peaks were presented in plots of relative permittivity versus temperature (ε _r − T ) with the sample of 0.01 ≤ x ≤ 0.04, which could be associated with composition fluctuation on account of the incorporation of Y₂O₃. The enhanced temperature stabilities of ferroelectric and piezoelectric properties were obtained in the temperature range from 20 to 140 °C. This result was found to be consistent with the change of dielectric properties. Besides, the outstanding electrical properties were obtained (d ₃₃ = 564 pC/N, k _p = 58 %, strain = 0.09 %, P _r = 8.38 μC/cm², ε _r = 3078, and tanδ = 0.03) at x = 0.02 due to the coexistence of orthorhombic and tetragonal phases.