Microstructure and piezoelectric properties of the CuO-added (Na0.5K0.5)(Nb0.97Sb0.03)O3 lead-free piezoelectric ceramics

The presence of the Sb5+ ion increased the piezoelectric properties of the (Na0.5K0.5)NbO3 (NKN) ceramics by enhancing the poling state as identified by the increased phase angle (theta). The increased theta value was explained by the increased ferroelectricity due to the large electronegativity of the Sb5+ ion and the increased off centering of the cation due to the small ionic size of the Sb5+ ion. The (Na0.5K0.5)(Nb0.97Sb0.03)O-3[NK(N0.97S0.03)] ceramics containing CuO were well sintered even at 960 degrees C. A small amount of the Cu2+ ions was incorporated into the matrix of the NK(N0.97S0.03) ceramic and behaved as a hardener. The k(p), Q(m), d(33), and epsilon(T)(3)/epsilon(0) values of the CuO-added NK(N0.97S0.03) ceramics were much higher than those of the CuO-added NKN ceramics due to the Sb5+ ion's enhancement of the piezoelectric properties by increasing the poling state of the specimens. The high piezoelectric properties of k(p)=0.41, Q(m)=1333, d(33)=111 pC/N, and epsilon(T)(3)/epsilon(0)=324 were obtained from the 2.0 mol % CuO-added NK(N0.97S0.03) ceramics sintered at 960 degrees C for 8 h. (c) 2008 American Institute of Physics.