Xinsen Zheng

Effect of La content on characterization of PLZT ceramics

Abstract This work has been undertaken with a view to study the effect of lanthanum content on properties of PLZT ceramics. The polycrystalline complex compounds of PLZT with Pb1−xLax(Zr0.40Ti0.60)1−x/4O3, +10% PbO formula were prepared from the nano-size individual oxides powders by hot-pressed process. Transparent PLZT (x/40/60) bulk ceramics with pure tetragonal phase was obtained. The studies of the microstructures, dielectric and ferroelectric properties of the ceramics were carried out. The experiment results showed that when La content increased from 7 to 13 mol.%, the grain size increased from 2 to 7 μm. La content also effects the dielectric property obviously, the dielectric constant increased with La content increasing. Moreover, the ferroelectric properties are sensitive to the variation of La content.

Preparation of PZT(53/47) thick films deposited by a dip-coating process

Crack-free polycrystalline PZT (PbZrTiO3) thick films up to 15 µm with perovskite structure have been prepared from a dip-coating process. The influence of substrate characteristics, withdrawal speed and ionic concentration of precursor solution on the morphology and microstructure of PZT film was examined. The dielectric, ferroelectric and piezoelectric properties of PZT thick films on Pt/Ti substrate were measured and evaluated. PZT(53/47) thick films on Pt/Ti substrate exhibits a excellent electric properties, e.g. Pr: 35 µC/cm2; Ec: 32 kV/cm; er: 830; tan δ: 0.01-0.03; d33: 142.

Martensitelike spontaneous relaxor-normal ferroelectric transformation in Pb(Zn1∕3Nb2∕3)O3–PbLa(ZrTi)O3 system

The spontaneous relaxor-normal ferroelectric transformation was found in the tetragonal composition of Pb(Zn1∕3Nb2∕3)O3–PbLa(ZrTi)O3 (0.3PZN–0.7PLZT) complex ABO3 system. The corresponding dielectric permittivities and losses of different compositions located near the morphotrophic phase boundary were analyzed. By reviewing all of the results about this type of transformation in previous references, the electric, compositional, structural, and thermodynamic characteristics of the spontaneous relaxor-normal transformation were proposed. Additionally, the adaptive phase model for martensite transformation proposed by Khachaturyan et al. [Phys. Rev. B 43, 10832 (1991)] was introduced into this ferroelectric transformation to explain the unique transformation pathway and associated features such as the tweedlike domain patterns and the dielectric dispersion under the critical transition temperature. Due to the critical compositions near the MPB, the ferroelectric materials just fulfill the condition, in which...

Normal-to-relaxor ferroelectric transformations in lanthanum-modified lead zinc niobate–lead zirconate titanate (PZN–PZT) ceramics

Dielectric permittivities of unpoled and poled lanthanum-modified lead zinc niobate–lead zirconate titanate (PZN–PZT) ceramics were investigated. Results showed that the relaxor characteristics were enhanced with an increase in La doping. Two characteristic temperatures Tnr (normal-to-relaxor transformation) and Trt (rhombohedral-to-tetragonal phase transition) were spontaneously observed in the poled specimens. Tnr and Trt both decreased with increasing La doping content. Temperature-dependent Sawyer–Tower polarization studies revealed a double hysteresis loop near Trt. The presence of the double hysteresis loop and the step in permittivity–temperature curves at Trt might imply a rhombohedral-to-tetragonal phase transition.

IMPRINT PROPERTIES OF YTTRIUM DOPED PZT THIN FILM

ABSTRACT Undoped and yttrium (Y) doped PZT (40/60) thin films have been deposited by spin-coating on Pt/Ti/SiO2/Si(100) substrates. The yttrium concentration, x, was varied from 1.5 to 3.5 wt% by 0.5 wt%. The annealing temperature and time of the thin films are 550–650°C for 5–10 min in 100% O2 atmosphere. The influence of the yttrium contents on the ferroelectric properties of PZT thin films has been studied. We investigated the imprint properties of Y-doped PZT (40/60) thin films at bias voltage and a temperature of 120°C. It is found that the imprint- resistant properties of the PZT thin films are enhanced by a suitable Y dopant concentration.

DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF PZN-PZT CERAMICS WITH NEODYMIUM DOPING

ABSTRACT The structure and electrical properties of Pb(Zn1/3Nb2/3)0.3(Zr0.55Ti0.45)0.7O3-xNd ceramics system with the composition near to the morphotropic phase boundary (MPB) were investigated as a function of Nd doping content. PZN-PZT specimens shifted from rhombohedral phase towards tetragonal phase with increasing Nd doping. Dielectric spectroscopy exhibited that Nd doping increased dielectric permittivity and the degree of diffuse phase transition (DPT) with lower ferroelectric phase transition temperature. The P-E curves showed that Nd doping decreased coercive field (Ec) and the remnant polarization (Pr).

Phase diagram for the 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb0.96La0.04 (ZrTi)0.99O3 solid solution in the vicinity of morphotropic phase boundary

The dielectric behaviours of numerous specimens near the morphotropic phase boundary (MPB) of the 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb0.96La0.04 (ZrxTi1 − x)0.99O3 (x = 0.50–0.53) relaxor ferroelectric system were measured. The results revealed that the poled specimens on the rhombohedral side underwent a rhombohedral–tetragonal transition on heating, and the depoled specimens on the tetragonal side experienced a spontaneous relaxor–normal transition on cooling. A phase diagram based on the dielectric permittivity measurements was proposed for this solid solution. The diagram showed that the polarization made the MPB bend sharply towards the rhombohedral-rich region. On the basis of these results in this and previous similar investigations, some common characteristics of complex relaxor ABO3 perovskite systems near the MPB were proposed.

OPTICAL AND PIEZOELECTRIC PROPERTIES OF TRANSPARENT PZN-PLZT CERAMICS

ABSTRACT 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb0.96La0.4(ZrxTi1−x)O3(PZN-PLZT, x = 0.5∼0.53) transparent piezoelectric ceramics with high density and pure perovskite have been synthesized by a two-stage hot-pressing procedure. The bulk densities of the specimens were measured by Archimedes method, and they are very close (> 99%) to the theoretical density. With the Zr/Ti ratios varying from 50/50 to 53/47, the d33 and kp show an ascending and descending trend, namely a peak of piezoelectric properties. The maximum of d33 and kp are 845pC/N and 0.70, respectively. The transmittances of the specimens were tested at the wavelength ranging from 300 nm to 800 nm. The transmittance of the specimens was enhanced with the increase of the wavelength. And the specimens with Zr/Ti = 52.5/47.5 have maximum transmittance. Transparence and high piezoelectric properties of PZN-PLZT brighten its application in optical and electrical devices.

Effects of Lanthanum Modification on the Structure and Electrical Properties of PZN-PZT Ceramics

La-modified PZN-PZT compositions with representative formula Pb1-0.7xLa0.7x(Zn1/3Nb2/3)0.3- (Zr0.55Ti0.45)0.7(1-x/4)O3 were prepared by the columbite precursor method. La content, x, was varied from 0 to 8mol%. Effects of La doping on microstructure, dielectric and piezoelectric properties were investigated. The results showed that in present system La doping promotes the formation of pyrochlore phase and the phase shifted from rhombohedral to tetragonal structure with increasing La content. It was also found that La doping makes dielectric permittivity maximum decrease and the degree of diffuse phase transition enhance. Appropriate amount of La doping could improve the piezoelectric properties.

Fabrication and Electrical Properties of Grain-Oriented 0.91Pb(Zn1/3Nb2/3)O3– 0.09PbTiO3 Ceramics

(200) grain-oriented 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 (PMN–0.09PT) piezoelectric ceramics with a degree of orientation of 0.5052 have been produced from melt by a directional solidification method. The dielectric, ferroelectric, and piezoelectric properties were investigated, e.g., ε~4200, tanδ~0.8%, d33~2100pC/N, kt~58%, and k33~90%, some of these values are comparable to those of ~PZN–PT single crystals. The strain–electric-field curve with a maximum strain of 0.49% at a field of 7kV/cm and well-saturated hysteresis loops with a Pr~32 mC/cm2 were recorded. The results demonstrate that the directional solidification method is a promising technique to fabricate high performance grain-oriented PZN–PT ceramics.