A high temperature stable piezoelectric strain of KNN-based ceramics

Lead-free (1 - x)(0.96K(0.46)Na(0.54)Nb(0.98)Ta(0.02)O(3)-0.04Bi(0.5)(Na0.82K0.18) 0.5ZrO3)-xCaZrO(3) ((1 - x)(0.96KNNT-0.04BNKZ)-xCZ) piezoelectric ceramics were prepared by the conventional solid-state reaction method. The CaZrO3 dopant can induce a coexisting phase boundary with the transition from the orthorhombic/tetragonal phase to the R phase. Domains that exist across the grain boundary within neighboring grains appear in the ceramics with x = 0.01, which can result in an increase in ferroelectricity due to its long-range order organization. The CaZrO3 dopant results in the formation of polar nanodomains and induces the appearance of diffuse ferroelectrics. The ceramics with x = 0.01 show optimal piezoelectric properties (d(33) = 300 pC N-1 and d*(33) = 500 pm V-1 at 25 kV cm(-1)). Meanwhile, their high level of unipolar strain reaches up to 0.175% at 35 kV cm(-1) at room temperature, and their field-induced strain varies less than 10% from room temperature to 120 degrees C. The ceramics with x = 0.02 possess a remarkably high temperature stability of d*(33) (T-e = 200 degrees C). For x = 0.005-0.025, a higher amount of the CaZrO3 dopant can obviously improve the temperature stability of d*(33): The (1 - x)(0.96KNNT-0.04BNKZ)-xCZ system is a promising lead-free piezoelectric candidate material for commercial applications.