Effects of CuO and ZnO Additives on Sintering Temperature and Piezoelectric Properties of 0.41Pb(Ni1/3Nb2/3)O3–0.36PbTiO3–0.23PbZrO3Ceramics

ZnO-added 0.41PNN–0.36PT–0.23PZ ceramics cannot be sintered below 950°C. However, when CuO is added, the liquid phase forms and specimens can be sintered even at 850°C. The dielectric constant ( ε T 3 / ε o ), piezoelectric constant ( d 33 ) and electromechanical coupling factor ( k p ) increase with the addition of CuO and this is due to the enhancement of the density of the specimens. When CuO is added to 0.41PNN–0.36PT–0.23PZ ceramics, improvements of density, ε T 3 / ε o , d 33 and k p are also observed. However, the d 33 and k p values of the CuO-added 0.41PNN–0.36PT–0.23PZ ceramics are less than those of the CuO- and ZnO-added specimens. Therefore, ZnO is effective in improving the piezoelectric properties of 0.41PNN–0.36PT–0.23PZ ceramics. Good dielectric and piezoelectric properties of d 33 =575(pC/N), k p =0.55 and ε T 3 / ε o = 3900 are obtained for 0.41PNN–0.36PT–0.23PZ+3.0 mol% ZnO with 1 mol% CuO sintered at 900°C for 2 h.