Features of dielectric response in PMN-PT ferroelectric ceramics

In this paper, electrical and structural properties were reported for pyrochlore free (1-x)[Pb(Mg1/3Nb2/3)O-3] - xPbTiO(3) (PMN-PT) (with 35 mol% PbTiO3) ceramics obtained from fine powders. Dielectric studies were focused on the investigation of the complex dielectric permittivity (epsilon '-i epsilon '') as a function of frequency and temperature. The effects of the dc applied electric field on dielectric response were also investigated. Results revealed a field dependence dielectric anomaly in the dielectric permittivity curves (epsilon(T)) in the low dc electric field region, which in turn prevails in the whole analysed frequency interval. To the best of our knowledge, these properties for the PMN-PT ceramic system have not been reported before as in this work. The results were analysed within the framework of the current models found in the literature.

Transições de fases estruturais em cerâmicas ferroelétricas do sistema PMN-PT

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da metodologia de síntese nas propriedades elétricas da cerâmica PMN-PT

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

(1-x)PMN-xPT ceramics prepared by conventional and modified columbite route: Effect on electrical properties

This study aims to demonstrate how the chemical homogeneity of B cations affects the microstructure and electrical responses of (1-x) PMN-xPT ceramics. Two methodologies were employed to synthesize three different compositions, with x assuming the values 0.10, 0.28, and 0.35. If compared to conventional method, the Ti-modified columbite route, which is characterized by higher B cation homogeneity, leads to PMN-PT powders and ceramics with lower content of PNT pyrochlore phase and, for 0.65PMN-0.35PT composition, minor amount of tetragonal phase is found. Conclusively, PMN-PT ceramics obtained by modified route favors B cations homogeneity, enhancing the dielectric, ferroelectric and piezoelectric properties.

The influence of thermal treatment on the preparation of PNM and PMN-PT thin films

Ferroelectric thin films belong to a class of materials with great technological importance in optic fibers, micro-electromechanical systems, and microprocessors and computers memories.The (1-x)PbMg1/3Nb2/3O3(x)PbTiO3 (PMN-PT) thin films, with x=0, 0.1, 0.35 and 0.5, were prepared by Pechini's process and deposited by spin-coating on Si(100), Pt/Ti/SiO2/Si(100) and quartz substrates. The goal of the present paper is to verify the thermal treatment influence on the perovskite phase formation, which is desirable for these applications. The phase formation was analyzed by X-ray diffraction. The film's surface was characterized by atomic force microscopy to analyze the roughness and the homogeneity. The results of this study indicate that the optimum conditions for obtaining the perovskite phase using a Pt/Ti/SiO2/Si(100) substrate, were drying each deposited layer at 140 degreesC (heating plate), and a final thermal treatment at 600 degreesC for 3 h in a closed system with a lead-rich atmosphere. (C) 2003 Elsevier B.V. All rights reserved.

Influence of seed particle frequency on the phase formation and on the microstructure of 0.88 PZN-0.07 BT-0.05 PT ceramic

The Pechini method as well as the simultaneous addition of seeds particles and dopant solutions of BaTiO3 (BT) and PbTiO3 (PT) were used to prepare the perovskite phase 0.88 PZN-0.07 BT-0.05 PT. To study the influence of seed particle frequency on the synthesis of the PZN ceramic, two ranges of seed particle size were used: the range from 30 to 100 nm, termed small seed particles (frequency of 10(15) particles/cm(3)); and the range from 100 to 900 nm, termed large seed particles (frequency of 10(13) particles/cm(3)). The crystalline nuclei size influenced the calcining process, the sintering process and the microstructure. Samples prepared with lower seed frequency displayed more amount of pyroclore phase, need higher temperatures for sintering and showed a more heterogeneous microstructure with poor dielectric properties. (C) 2000 Elsevier B.V. Ltd and Techna S.r.l. All rights reserved.

Síntese de filmes finos do sistema PMN-PT pelo método dos precursores óxidos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudo de transições de fases estruturais nos sistemas PZT e PMN-PT por espectroscopia no infravermelho e espectroscopia de impedância

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e propriedades físicas de cerâmicas ferroelétricas de PMN-PT

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Study of Ti-modified columbite route and the effect of lithium doping in 0.9PMN-0.1PT ceramics

The influence of lithium on the structural characteristics of PMN-PT ceramic was studied. The synthesis of PMN-PT powders using this precursor leads to the formation of high amount of perovskite phase. The insertion of Li(+) ions in B-site affects the microstructure because the rise in mass transport changes the mechanical characteristics of sintered ceramic. Higher values of K(m) and T(m) were gotten when lithium is inserted into perovskite phase. Secondary phase was found when lithium content increase beyond 1 mol%, besides the occurrence of transgranular fractures in sintered ceramic. Also, the additive acts increasing the relaxor behavior.

Synthesis of slightly < 111 >-oriented 0.65Pb(Mg1/3Nb2/3)O-3-0.35PbTiO(3) ceramic prepared from fine powders

Slightly < 111 >-oriented 0.65Pb(Mg1/3Nb2/3)03-0.35PbTiO(3) ceramic was prepared using fine powders obtained by means of an alternative and promising chemical oxide precursor method. High quality samples with improved structural, microstructural, dielectric and ferroelectric properties were obtained. The dielectric constant value (epsilon similar to 2577) measured at 1 kHz is compared to unpoled < 112 > grain-oriented ceramics while the remanent polarization (P-r similar to 19-1 mu cm(-2)) is compared with random grain-oriented ceramics. These results point out the viability to produce ferroelectric PMN-PT ceramics of very good quality using powder precursors prepared from this chemical method. (c) 2007 Elsevier B.V. All rights reserved.

Structural Phase Transition Studies on PMN-0.35PT using Infrared Spectroscopy

The purpose of the present work is to report studies on structural phase transition for PMN-xPT ferroelectric, with melt PbTiO3 composition around the MPB (x = 0.35 mol %), using infrared spectroscopy technique. The study was centered on monitoring the behavior of the 1-(NbO), 1-(TiO) and 1-(MgO) stretching modes as a function of temperature. The increasing as a function of temperature for 1-(TiO) and 1-(MgO) modes, observed between 230 and 300 K, can be related to the monoclinic (MC) + tetragonal (T) phase coexistence in the PMN-PT.

Structural Phase Transition Studies on PMN-0.35PT using Infrared Spectroscopy

The purpose of the present work is to report studies on structural phase transition for PMN-xPT ferroelectric, with melt PbTiO3 composition around the MPB (x = 0.35 mol %), using infrared spectroscopy technique. The study was centered on monitoring the behavior of the 1-(NbO), 1-(TiO) and 1-(MgO) stretching modes as a function of temperature. The increasing as a function of temperature for 1-(TiO) and 1-(MgO) modes, observed between 230 and 300 K, can be related to the monoclinic (MC) + tetragonal (T) phase coexistence in the PMN-PT.

Characterization of the columbite precursor and (1-x)PMN-xPT powders prepared by Ti-modified columbite route

This study proposes to synthesize (1-x)PMN-xPT powders, where 0.10 < x < 0.45, using the T-modified columbite route. This methodology consists in the preparation of the MNT columbite precursor via the polymeric precursor method, followed by the solid state reaction with PbO to get the PMN-PT powders. It was verified that from 15 mol% of Ti, the MNT presents the coexistence of two main phases with different crystal symmetry: Rutile and Columbite. However, the synthesis of (1-x)PMN-xPT powders is not affected by this event. A detailed study of structural effects in MNT and PMN-PT powders as function of Ti content was made using the Rietveld method. It was also demonstrated that powders possess high chemical and microstructural homogeneity.

Structural characterization of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) powders

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate-lead titanate (PMN-50PT). Ab initio study of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) ceramic powders, with x = 0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic-tetragonal phases in the system. It was verified that even for 40 mol% of barium, it was possible to obtain pyrochlore-free PMN-PT powders. The increase of the lattice parameters of PMN-PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120 nm for 40 mol% of barium against 167 mn for the pure sample. Although high barium content (40 mol%) was deleterious for a dense ceramic, contents up to 20 mol% allowed 95% density when sintered at 1100 degrees C for 4 h. (c) 2007 Elsevier Ltd. All rights reserved.