Jianzhou Du

Effects of the Calcining Temperature on the Piezoelectric and Dielectric Properties of 0.55PNN-0.45PZT Ceramics

The 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 (0.55PNN-0.45PZT) ceramics were prepared by conventional solid state reactions. The effects of calcining temperature on the particle size and piezoelectric properties of 0.55PNN-0.45PZT piezoelectric ceramics were investigated. The particle size and crystallinity of 0.55PNN-0.45PZT ceramic powders are influenced by calcining temperature, and therefore the microstructure and final piezoelectric properties of 0.55PNN-0.45PZT are different. The highest piezoelectric properties (d 33 = 720pC/N, k p = 0.55. ϵ r = 6255) were observed at the sample fabricated from the powder calcined at 1100°C, which was attributed to the improved crystallinity and the homogeneous distribution of the particles.

Temperature stability and fabrication of Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 fibers with Pt core

In order to improve the electrical properties of metal-core piezoelectric ceramic fibers at high temperature, Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 piezoelectric ceramics with high Curie temperature were selected. The Pb(Zn1/3Nb2/3) O3–Pb(Zr,Ti)O3 metal-core piezoelectric ceramic fibers were successfully fabricated by extrusion Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 powder around a platinum wire. The microstructure and electrical properties of Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 ceramics with different calcining and sintering temperatures were investigated. Compared with the previous metal-core piezoelectric ceramic fibers, the Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 fibers showed lower piezoelectric and dielectric properties ( ε 33 T = 1272 , k31 = 0.253, and d31 = −120 pC N−1). However, the Curie temperature of Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 ceramics is about 295°C, much higher than that of 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 ceramics (110°C). The Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 fibers can be used at the highest temperature of 150°C, and the temperature stability of Pb(Zn1/3Nb2/3)O3–Pb(Zr,Ti)O3 fibers is much better than that of 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3 fibers.

Fabrication and characterization of relaxor-ferroelectric 0.55Pb(Ni 1/3 Nb 2/3 )O 3 -0.45Pb(Zr 0.3 Ti 0.7 )O 3 ceramics with sintering aid

A traditional solid-state sintering method was used to fabricate 0.55Pb(Ni_1/3Nb_2/3)O₃-0.45Pb(Zr_0.3Ti_0.7)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 ABO₃ structure 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 ρ~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, k_p~55%, ε₁ r~7365, tanδ~2.9%, p_r~18.86 μC/cm², and E_c~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.

Electrical properties and sensing ability of novel piezoelectric ceramic fibers with Pt core

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 Fe2O3 significantly improved the microstructure and electrical properties. Compared with pure PNN-PZT ceramics, higher dielectric and piezoelectric properties of d31~-390 pC/N, ε 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 ε 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.