Papers by Keyword: PLZT

Abstract: PLZT (X/70/30) ceramics with different La contents (X=7.45, 7.54, 7.63 mole%) were fabricated by hot-press sintering techniques. The effects of annealing on ferroelectric, optical and electrically controlled light scattering properties of PLZT transparent ceramics were examined and analyzed. The XRD patterns indicated that all the samples were crystallized into a pure perovskite phase without the second phase. The SEM exhibited fully dense, uniform microstructures with well-developed grains. The annealing treatment weakened the degree of squareness of the ferroelectric hysteresis loop, and even the anti-ferroelectric phase occurred as the La content increasing to X=7.63. The remnant polarization (Pr) and coercive electric field (Ec) decreased with the annealing treatment for all samples. The slow annealing treatment resulted in the lager increase of both transmittance and contrast ratio than those of the rapid annealing treatment at λ=632.8nm. The electrically controlled light scattering properties were obviously enhanced by the annealing treatment. Especially, the PLZT (7.63/70/30) ceramics exhibited the different electrically controlled light scattering performance which indicated it could hold high transmittance and symmetry in a wide electric field range with the slow annealing treatment.

Abstract: In the present work the influence of co-doping with ytterbium ions (for 0, 0.5, 1.5, 2.5 wt.% of Yb³⁺) on physical properties of 8/65/35 PLZT was studied. The ceramic powders were synthesized by the modified sol-gel method, and underwent consolidation by the pressure-less sintering techniques, in Ts=1200°C/6h. Our investigations give a detailed account of the relationships between concentrations of trivalent ytterbium ions in PLZT matrix, on their structure, microstructure, as well as luminescence properties. Near-infrared luminescence spectra at about 1020 nm were registered, which correspond to ²F_5/2 - ²F_7/2 transition of Yb³⁺. Based on decay measurements, the luminescence lifetimes for the ²F_5/2 excited state of Yb³⁺ were determined. Luminescence decay analysis indicates that the ²F_5/2 lifetime increase with increasing activator concentration (Yb³⁺) in PLZT ceramic matrix.

Abstract: The lanthanum-modified lead zirconate titanate transparent ceramics with different Zr/Ti ratio were prepared by the hot pressing sintering method. A single perovskive structure with a dense microsctructure was obtained and the transgranular fracture of PLZT ceramics tended to be more serious As the Zr/Ti ratio increases, the transmittance of PLZT ceramics tended to be higher and the transgranular fracture became more serious. The P-E loops changed froe a square hysteresis loop to a double tending slim hysteresis loop. Besides,the S-E loops changed from a approximate parabolic shape to a butterfly shape. These two loops confirm the transition from normal ferroelectric to anti ferroelectric phase occured with the Zr/Ti ratio increasing.

Abstract: Structure–property relationship has been performed in the lanthanum-modified lead–zirconate–titanate (PLZT) with a lanthanum content 8 and Zr/Ti ratio 40/60. The X-ray diffraction analysis, scanning electron microscopy, and sintering behavior have evidently demonstrated that it is possible to tailor the structural properties of PLZT 8/40/60. Structure of PLZT 8/40/60 had pure perovskite with tetragonal without secondary phase. Tetragonality (c/a) was observed in the range of 1.01093-1.02095. SEM micrographs were shown a development of mean grain size to clarify the development of grain after sintering processing. The result shows that increasing of sintering temperature resulted in mean grain size increasing from 1.70 to 3.08 μm. Ferroelectricity of PLZT ceramics were normal ferroelectric and dielectric constant increased with the increasing sintering temperature.

Abstract: Feroelectric lead lanthanum zirconate titanate (PLZT) ceramics 9/70/30 were synthesized by conventional mixed-oxide method via a vibro-milling technique. The effect of sintering temperature and two-stage sintering method on electrical properties of PLZT ceramics was investigated. The ceramic powder was uniaxially pressed in pellets and sintered at the temperatures ranging from 1200 to 1275 °C for 4hrs and two-stage sintering temperature at 1200 °C for 4 hrs. Dielectric, ferroelectric and strain properties of ceramics were characterized by LCR meter, modified Sawyer–Tower Circuit and modified Michelson interferometric technique respectively.

Abstract: In this study, Pb_0.91La_0.09(Zr_xTi_1-x)O₃ ceramics ( x = 0.75, 0.70, 0.65, 0.60, 0.55 and 0.50) have been synthesized by conventional mixed oxide method via a vibro-milling technique. The effect of composition on phase formation and electrical properties of PLZT ceramics was investigated. All compositions of powders were uniaxially pressed in pellets and sintered at the temperatures of 1275°C for 2h. Phase formation, dielectric, ferroelectric strain properties of ceramics were characterized by XRD, LCR meter, modified Sawyer–Tower Circuit and modified Michelson interferometric technique respectively. In this study new materials will be systematically developed based on the material engineering approach (processing vs electrical properties).

Abstract: Lead lanthanum zirconate titanate (PLZT) transparent ceramics have attracted more and more attentions for their unique electric-induced light scattering effects. The PLZT ceramics of 7.45 mole% lanthanum with different Zr/Ti ratios (Zr/Ti=68/32, 69/31, 70/30, 71/29, 72/28) were prepared by the hot-press sintering method. The X-ray diffraction patterns confirm that all the PLZT samples are perovskite structure without detected secondary phases. The SEM images of the fracture surfaces of the samples show that all the PLZT materials tend to fracture transgranularly, and exhibit fully dense and uniform microstructures. All the samples with different Zr/Ti ratios present typical relaxation ferroelectric phase transition characteristics with square shaped hysteresis loops. Noticeably, all the original PLZT samples show an excellent transparency in the wavelength range from visible to near-infrared, and they will become opaque after an appropriate electric field experienced. The opaque sample can also recover to the transparent state when an inverse compatible electric field acts on it. The contrast ratio of the sample increases firstly and then decreases when the Zr/Ti ratio increases from 68/32 to 72/28 (λ=632.8nm). The PLZT (7.45/70/30) material shows a maximum contrast ratio, which makes it promising to apply in optical modulators.

Abstract: La_0.67Sr_0.33MnO₃ (LSMO)/Pb_0.92La_0.08Zr_0.65Ti_0.35O₃ (PLZT) composite film was fabricated on a (001) LaAlO₃ (LAO) single crystal substrate by a sol-gel technique. The results from X-ray diffraction (XRD) indicated that LSMO and PLZT could grow successively on LAO substrate with (001) preferred orientation. The ferroelectric and ferromagnetic properties of LAO/LSMO/PLZT composite film were also investigated. The results showed that the remnant polarization P_r, and coercive field E_c of the composite film at room temperature were 36.38 μC/cm² and 512.43 kV/cm respectively. Moreover, the composite film exhibited significant ferromagnetic hysteresis loops and soft magnetic behavior at temperatures lower than 250 K.

Abstract: This paper describes the relationship between sintering time conditons, tetragonality from phase formation, dielectric and ferroelectric characteristics of tetragonal PLZT (lanthanum modified lead zirconate titanate) ceramics with the pressureless sintering conditions. Ferroelectric compounds of Pb_0.92La_0.08(Zr_0.4,Ti_0.6)_0.98)O_3, PLZT 8/40/60, were prepared using mixed-oxide synthetic route via a rapid vibro-milling method. X-ray diffraction, is used to observe the tetragonality characteristic and the presence of pyrochlore. When sintering time was increased (≥ 8 hours), pyrochlore was developed. It can be observed that with the increased sintering time, it were changed the structure and ferroelectric behavior of the PLZT ceramics.

Abstract: In this paper the effect of lanthanum addition on the phase formation, dielectric and ferroelectric characteristics of x/65/35 PLZT. This ceramics were prepared using mixed-oxide synthetic route via a rapid vibro-milling method. All samples were sintered at 1200°C for 12 h. X-ray diffraction was used to observe the crystal structure. It was found that when increasing lanthanum content, the structure remained rhombohedral. It can be seen that the change of behavior to ferroelectric relaxor with the increasing of lanthanum content resulted in the change of elastic strain