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The traditional sintering method was used to sinter the pure and Fe2O3 doped 0.55Pb(Ni0.33Nb0.67)O3-0.45Pb(Zr0.3Ti0.7)O3(abbreviate as PNN-PZT and PFNN-PZT, respectively) ceramics. The addition of Fe2O3significantly improved the microstructure and electrical properties. Compared with pure PNN-PZT ceramics, higher dielectric and piezoelectric properties of d31~-390 pC/N, r~6298 were obtained for the PFNN-PZT sample sintered at 1175°C for 2 h. Hence, the PFNN-PZT ceramics sample was selected to fabricate piezoelectric ceramic fibers with Pt core (PFC). Both the green fibers and bulk ceramics were sintered at 1150-1225°C for 2 h in a closed crucible, respectively. The effect of sintering temperature on the microstructure and electrical properties of the PFNN-PZT fibers was investigated. The optimal piezoelectric properties are obtained for the sample sintered at 1175°C for 2 h. The relative dielectric constant and piezoelectric constant show peak values of r~3683, d31~-197.4 pC/N, respectively. The PFC is a new type piezoelectric device, which can be used for sensors or actuators. The results of sensing experiment show that the piezoelectric ceramic fiber with Pt core has high sensitivity for the Lamb waves.

A traditional solid-state sintering method was used to fabricate 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr0.3Ti0.7)O3(0.55PNN-0.45PZT) relaxor-ferroelectric ceramics with CuO as sintering aid. The influence of xCuO additions (x=0.0, 0.2, 0.4, 0.6, 0.8 wt.%) on the microstructure and electrical properties of the 0.55PNN-0.45PZT ceramics was investigated. X-ray diffraction patterns demonstrated that all specimens formed a typical perovskite structure with pseudo-cubic phase. Cu2+ions entered into the B sites in ABO3structure for the PNN-PZT solid solution ceramics. The additions of CuO improved the sinterability of the 0.55PNN-0.45PZT ceramics. The grain size and density of these specimens increased slightly with increasing amounts of CuO addition. The specimen with 0.4 wt.% CuO addition achieves the maximum value of density ~8108 kg/m3. Meanwhile, the piezoelectric, dielectric and ferroelectric properties also enhanced significantly with increasing amount of CuO addition. Excellent properties, d33~777 pC/N, kp~55%, 1r~7365, tan~2.9%, pr~18.86 C/cm2, and Ec~3.52 kV/cm were obtained for the 0.55PNN-0.45PZT ceramics with 0.4 wt.% CuO addition sintered at 1125°C for 2 h.