Papers by Keyword: Relaxor Ferroelectric

Abstract: Undoped barium titanate and lanthanum (La) doped barium titanate (BaTiO₃) were studied for ferroelectric properties with the formula of Ba_1-xLa_xTi_1-x/4O₃ for x=0.1 and being prepared by using conventional solid state method reaction. The pure phase of this composition which x=0 were found at final heating temperatures starting from 1300°C and x=0.1 at 1350°C for overnight in air with intermittent grinding. The changes in the crystal structure of the composition were detected by using X-ray diffraction. Impedance Spectroscopy analysis is carried out to determine the dielectric properties for undoped BaTiO₃ and La doped BaTiO₃ for x=0.1.

Abstract: La-doped barium titanate (BaTiO₃) was prepared using conventional solid state synthesis route. All peaks for sample x=0 are approaching the phase pure of BaTiO₃ structure with tetragonal crystal structure (P4mm). Sintering of pressed powder are performed at 1300oC, 1400oC and 1450oC for overnight for pure BaTiO₃ and 1350oC for 3 days for BaTiO₃ doped lanthanum with intermittent grinding. Phase transition was studied by different x composition. The changes in the crystal structure of the composition x=0.1 and 0.2 were detected by using X-ray diffraction (XRD). The phase changes between tetragonal-cubic and cubic-tetragonal depending on the temperature. Rietveld Refinement analysis is carried out to determine the lattice parameter and unit cell for BaTiO₃.

Abstract: Lanthanum doped barium titanate (BaTiO₃) were studied for high-K dielectric and exhibit a relaxor ferroelectric properties and it can be prepared by using various method. Relaxor ferroelectric offers a wide temperature and frequency range of application for materials with high dielectric constant for microelectronic application. This paper reviews the preparation methods, the important features, advantages and limitation for the lanthanum doped barium titanate. Thus, the phase purity and mixture selected also been review on the second part of the article. The article concludes with a brief discussion of the methods with good dielectric behavior. The objectives of this paper are to determine the selection of suitable preparation methods and the properties of the high-K dielectric based on pure barium titanate and lanthanum doped barium titanate.

Abstract: 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 P_s (saturation polarization) was significantly higher.

Abstract: First ferroelectric materials were found in Rochelle salt was in a perovskite structure. Lead Magnesium Niobate (PMN) is a perovskites with a formula of PbMg_1/3Nb_2/3O₃ (PMN) and are typical representatives for most of all ferroelectrics materials with relaxor characteristic. It posses high dielectric permittivity which nearly ~ 20,000[ with a broad dielectric permittivity characteristic, known as relaxor ferroelectric below room temperature. Some of the researcher might think that the transition from relaxor ferroelectric to paraelectric is similar to the characteristic as observed from ferroelectric to paraelectric, but it is not necessary. The puzzling is how do we categorise them. How is the domain structure look like typically in ceramic materials.

Abstract: A new system, Bi_1.3Yb_0.7O₃-BaTiO₃ was found as a perovskite dielectrics with some advantageous properties. The structure was identified by X-ray diffraction method and SEM was also employed to observe the surface and fracture morphologies. The studies indicate that the relative dielectric constant initially increases and then decreases slightly, the dielectric loss initially decreases and finally close to a stable value. The experimental results reveal that the grain size became smaller initially, then increase after the sample E and finally the sample F had the maximum grain size. Experiments show the system Bi_1.3Yb_0.7O₃-BaTiO₃ can significantly improve the thermal stability of the BaTiO₃ ceramics. Electric hysteresis loop show that the system is relaxor ferroelectric. The samples doped with 20% BiYbO₃ calcined at 750°C for 2h and then sintered at 1280°C for 2h exhibited attractive properties, including high relative dielectric constant (>1000), low dielectric loss (<2.5%), low temperature coefficient of capacitor (<±15%) over a wide temperature range from －55°C to +180°C, satisfying EIA X8R specifications.

Abstract: We synthesize polycrystalline Sr1-xPbxTiO3 (SPT) (0

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