Low temperature sintering and role of room-temperature phase transition in the electrical properties of (Ba0.85Ca0.15)(Zr0.10Ti0.90)1−x(Cu1/3Nb2/3)xO3 ceramics

Abstract

Perovskite type (Ba0.85Ca0.15)(Zr0.10Ti0.90)1−x(Cu1/3Nb2/3)xO3 (x = 0.00, 0.005, 0.01, 0.015 and 0.02) (abbreviated as BCZT-1000xCN) lead-free ceramics were prepared via a conventional solid-state reaction method. The phase structure, microstructural morphology and electrical properties of BCZT-1000xCN ceramics with different CuO/Nb2O5 content were systematically investigated. The phase identifications of the ceramic samples were investigated by X-ray diffraction and the results indicated that all samples showed a pure perovskite phase with no secondary phase. Microstructure, electrical properties and polarization–electric field (P–E) hysteresis loops indicated that a small amount of CuO/Nb2O5 (x = 0.005–0.02) addition affected the properties obviously. The addition of CN effectively resulted in the decrease of grain sizes and slightly improved uniformity of grains in BCZT ceramics. Moreover, the results revealed that the addition of CN significantly improved the sinterability of BCZT ceramics which resulted in a reduction of sintering temperature from 1450 to 1400 °C without sacrificing the high piezoelectric properties. Achieving a polymorphic phase transition point at room temperature about 20 °C could improve the piezoelectric properties of BCZT-1000xCN ceramics. Main piezoelectric parameters of BCZT-1000xCN ceramics were optimized around x = 0.01 with a high piezoelectric coefficient (d 33 = 550 pC/N), a planar electromechanical coefficient k p of 50%, a remnant polarization (P r = 12.6 μC/cm2), a high dielectric constant (e rmax = 6056) and a low dissipation factor (tanδ = 1.55%) at 1 kHz, indicating promising applications for lead-free piezoelectric ceramics.