Xiyun He

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.

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.

Effect of anisotropy on the ferroelectric, optical, and electro-optic properties of PLZT transparent ceramics prepared by uniaxial hot-press sintering techniques

PLZT (X/70/30) ceramics with different La contents (X = 7.45, 7.51,7.57, 7.63) were fabricated to study the effect of anisotropy on ferroelectric, optical, and electro-optic properties in parallel and normal to the uniaxial hot-press sintering direction (abbreviated as parallel and normal), respectively. All samples show the square hysteresis loops but the tetragonality with ferroelectricity is more evident in a parallel direction than that in normal direction. The high transmittances (≥60%, 0.35mm, visible to near infrared light) are obtained. However, the transmittances and the light scattering contrast ratios are higher in the normal direction. The PLZT (7.63/70/30) ceramic exhibits the more stable electrically controlled light scattering behavior in parallel direction and its contrast ratio reaches to the maximum 1.37 in a normal direction in this system.

Magnetic and Electrical Properties of Zr-rich (1-x)PZT+xBiFeO3 Ceramics

We reported multiferroic ceramics (1-x)PZT +xBiFeO3 (x = 0.01–0.10, Zr/Ti = 95/5–100/0) were prepared by a conventional solid-state reaction process. The structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD showed that the (1-x)PZT+xBiFeO3 samples formed perovskite structure. SEM indicated that the dense ceramics were obtained when the sintering process was modified. It is well known that the PZT95/5 system is a typical ferroelectric material and BiFeO3 possesses antiferromagnetic property. It was found that (1-x)PZT+xBiFeO3 exhibited both ferroelectric and ferromagnetic properties at room temperature. The relationship between the ferroelectric and ferromagnetic properties was discussed.

Light Scattering Properties for PLZT Transparent Ceramics of Different Zr/Ti Ratios

Lead lanthanum zirconate titanate (PLZT) transparent ceramics present an attractive electrically controlled light scattering performance with high transmittance and large contrast ratio. PLZT ceramics of 8 mole% lanthanum with different Zr/Ti ratios (Zr/Ti=68/32, 70/30, 72/28) were prepared by the hot pressing method to figure out the influence of Zr/Ti ratios to the light scattering performance. X-ray diffraction patterns confirm that all the samples are perovskite structure with no secondary impurity phase detected. All the three compositions show double tending slim hysteresis loops which due to antiferroelectric phase coexisted. Besides, within the range of near-infrared to ultraviolet wavelength, all the PLZT samples show high transmittance. While the Zr/Ti ratio increasing from 68/32 to 72/28, the transmittance reduced value RT of the sample decreases gradually (λ: 632.8 nm). PLZT (8/68/32) sample shows a maximum RT, it promises a good application in optical modulators, goggles and so on.

Effects of Eu3+ Substitution on Nanosized Mn-Zn Ferrite Powders Synthesized by Combustion Processing

A series of Eu3+-substituted Mn 0.65 Zn 0.35 Fe 2-x EuxO4 ( x = 0.00-0.04) nanoscaled ferrites were synthesized by a citrate sol-gel combustion processing. The effects of Eu 3+ substitution on the crystalline formation, microstructure and magnetic properties of Mn-Zn ferrite annealing at temperature from 500°C to 800°C were investigated. The results showed that the lattice parameter increased and it contributed to monophase spinel with the addition of Eu 3+ at x≤ 0.03. The remanence and coercive field increased with Eu 3+ substitution but it changed slightly in saturation magnetization when annealing ferrite powders at 700°C.

Dielectric Property of Functionally Graded Ferroelectric PZT Ceramics

Ferroelectric material possesses a high dielectric constant during ferroelectric to paraelectric phase transition. But, the high dielectric constant exhibits only within a very small temperature window because the phase transition region is narrow. Functionally graded material is suggested to enlarge the phase transition region. Here, both functionally graded ferroelectric ceramics lead titanate zirconate(PZT) and PZT with single composition are prepared. Dielectric property in two systems is measured and compared each other. Functionally graded ceramics PZT possesses a relatively high dielectric constant within a large temperature range. It is due to the FGM PZT has a wide phase transformation temperature region.

Influence of Film Thickness on Optical Properties of PLZT Thin Films Derived from MOD Method

PLZT (9/65/35) thin films on sapphire (001) substrates with thickness of 0.1 ~ 0.9 µm were prepared by a metal-organic decomposition (MOD) process. All the films present highly (110)-preferred orientation independent of the film thickness. The microstructure of the films was investigated. The influence of film thickness on optical properties of PLZT films was examined and analyzed. As the film thickness is increased, the absorption edge of the film is shifted to longer wavelength; the optical band gap Eg is increased slightly. The refractive index at 510nm determined from optical transmission spectra also shows an increasing tendency as film thickness increasing. Great stress aggregated during the film preparing process is thought to be an important reason which results in the variations of optical properties of the films with different thickness.

Fabrication, Microstructure and Magnetic Properties of LiZn Ferrites by Hot Pressing Method

The effects of sintering temperature on microstructure, phase, electrical and magnetic properties of LiZn ferrites prepared by hot pressing methods were examined systematically. All the ferrites were spinel strustures sintered at the temperature above 1050°C. At higher than 1100°C, pores within the grains appeared due to the volatilization of lithium. The DC electrical resistivity ρ increased firstly and decreased dramatically because of the Fe2+ formation. The magnetic properties showed that the saturation magnetization (Ms) increased and coercive field (Hc) decreased with the increasing temperature. The hot pressing method is proven an effective way to obtain the densified LiZn ferrites.

A Comparative Research on PLMNT Relaxor Ferroelectric Ceramic Prepared by Conventional and Hot-Press Techniques

PLMNT3/75/25 ceramics were prepared by uniaxial hot-press sintering method and conventional sintering method, respectively. X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer were used to measure the properties of the PLMNT ceramics. PLMNT ceramic with pure perovskite phase was fabricated by uniaxial hot-press sintering method, while, a secondary pyrochlore phase was found in PLMNT ceramic prepared by conventional sintering method. It was observed that the PLMNT ceramic fabricated by uniaxial hot-press sintering showed better densification and more uniform grain size than that of the PLMNT ceramic prepared by conventional sintering. The dielectric responses showed that the samples prepared by two methods both exhibited diffuse phase transition characteristic, and the values of the diffusivity parameter were calculated according to the linear fitting of the modified Curie-Weiss law. The relaxor ferroelectric characteristics of PLMNT ceramics accorded well with the Vogel-Fulcher relationship. The P-E hysteresis loops of the samples from uniaxial hot-press sintering were apparently slight than that of conventional sintering samples, while the value of the Ps (saturation polarization) was significantly higher.