Xuming Pang

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.

Influence of sintering temperature on electrical properties of (K 0.4425 Na 0.52 Li 0.0375 )(Nb 0.8825 Sb 0.07 Ta 0.0475 )O 3 ceramics without phase transition induced by sintering temperature

Lead-free (K0.4425Na0.52Li0.0375)(Nb0.8825Sb0.07Ta0.0475)O3 (KNLNST) piezoelectric ceramics are synthesized by the conventional solid-state reaction method. The sintering temperature and poling temperature dependence of ceramic properties are investigated. Previous studies have shown that variation of sintering temperature can cause phase transition, similar to the morphotropic phase boundary (MPB) behavior induced by composition changes in Pb(Zr,Ti)O3 (PZT). And the best piezoelectric performance can be obtained near the phase-transition sintering temperature. In this research, phase transition induced by sintering temperature cannot be detected and excellent piezoelectric properties can still be obtained. The sintering temperature of the largest piezoelectric coefficient of such composition is lower than that of the highest density, which is considered in composition segregation as a result of intensified volatilization of alkali metal oxides. Combined with the effect of poling temperature, the peak values of the piezoelectric properties are d33 = 313 pC/N, kp = 47%, ɛr = 1825, tan δ = 0.024, To-t = 88 °C, and TC = 274 °C.

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.

Synthesis and Characterization of (K0.5Na0.5)NbO3 Piezoelectric Ceramics Prepared Using K5.70Li4.07Nb10.23O30 as a New Sintering Aid

K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramics containing 1 mol% ZnO (KNNZ) were prepared by optimizing the sintering conditions using the newly developed K5.70Li4.07Nb10.23O30 (KLN) as a sintering aid. The phase structure and electrical properties of the KNNZ ceramics were investigated as a function of the KLN concentration. The results show that a small amount of KLN was incorporated into the lattice and formed a single-phase perovskite structure. The KLN modification lowered the phase transition temperature of the orthorhombic–tetragonal structure and increased the Curie temperature. Interestingly, an appropriate amount of KLN can simultaneously improve the sinterability of the KNNZ ceramics and the ferroelectric and piezoelectric properties. Good piezoelectric and dielectric properties (piezoelectric constant, d 33 = 131 pC/N; planar coupling coefficient, k p = 0.42; dielectric constant, ϵ r = 634; and mechanical quality factor, Q m = 20) were obtained for the KNNZ ceramics doped with 1 mol% KLN. Therefore, KNNZ + 1.0 mol% KLN ceramics containing an appropriate amount of KLN are good candidate materials for the preparation of lead-free piezoelectric ceramics.

Microstructure and piezoelectric properties of K 5.70 Li 4.07 Nb 10.23 O 30 -added K 0.5 Na 0.5 NbO 3 ceramics

Lead-free piezoelectric ceramics K0.5Na0.5NbO3-xmol%K5.70Li4.07Nb10.23O30 (x = 0–2.5, KNN-xmol%KLN) were prepared by conventional sintering technique. The phase structure and electrical properties of KNN ceramics were investigated as a function of KLN concentration. The results showed that small amount of KLN introduced into the lattice formed a single phase perovskite structure. The KLN modification lowered the phase transition temperature of orthorhombic-tetragonal (TO-T) and increased the Curie temperature (TC). Some abnormal coarse grains were formed in a matrix when the content of KLN was relatively low (1 mol%). However, normally grown grains were only observed when the sintering aid content was increased to 2 mol%. Proper content of KLN decreased the amount of defects, thus the remanent polarization increased and the coercive field decreased markedly, and the sinterability of the KNN ceramics was simultaneously improved with significant increase of piezoelectric properties.