PMN Powder Research Articles

The processing and characterization of Pb(Mg1/3Nb2/3)O3 (PMN) powders for coating capacitor

The present paper extensively demonstrates synthesis, characterization and electrical properties of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) sub-micron powders and PMN coatings on n-type Si substrates using sol–gel technique for capacitor applications. Transparent solutions were prepared from Pb, Mg and Nb based precursors, methanol and glacial acetic acid (GAA). The obtained solutions were dried at 80°C for 60min in air to form gel structure of PMN mixture and heat treated at 530°C for 3h and subsequently annealed at the temperature range of 800°C and 1000°C for 2h in air. After the sintering, the PMN powders were milled for 24h to obtain sub-micron powders. The powder size was measured using particle size machine. Finally, the powders were dispersed in alcohol and the obtained suspension was coated on n-type Si substrates. The films were dried at 50°C for 15min and subsequently were heat treated at 730°C for 30min in air to ensure its adhesion strength. Thermal, structural, microstructural, mechanical and electrical properties of the powder and the coatings were characterized by differential thermal analysis-thermo gravimeter (DTA/TG), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), refractometer, spectrophotometer and high resolution dielectric analyzer machines. The study provides a new insight on the sub-micron powders of PMN structure coated on Si semiconducting surface.

Effective dielectric function of porousPb(Mg1/3Nb2/3)O3ceramics

A set of $\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ (PMN) relaxor ceramics with different porosities (66--96% of theoretical density) was processed from the pure perovskite PMN powder by varying the sintering temperature (930--980 K) and isostatic pressure. The effective room temperature permittivity at 100 Hz varied correspondingly from \ensuremath{\sim}4000 to \ensuremath{\sim}15 000. We measured and fitted the room temperature infrared (IR) reflectivity of corresponding polished ceramics, from which the effective dielectric function was obtained. The results were compared with the low-frequency permittivity data and discussed using several effective medium models. The best results were obtained using the Lichtenecker model (with the exponent \ensuremath{\alpha} \ensuremath{\approx} 0.2), which fits quite well the IR spectra as well as the static permittivity for all the porosity values. Also the simulation using the finite element method supported the same model. It allows us to conclude that the samples show quite complex shape and topology of the pores, but all of the pores show similarity with a weak nonzero percolation (open porosity).

Synthesis of Pb(Mg1/3Nb2/3)O3 by Self‐Assembled Colloidal Aggregates

We developed a new, simple method to prepare pure perovskite Pb(Mg1/3Nb2/3)O3 (PMN) from an aqueous suspension in a single annealing step. In this synthesis it is crucial to suppress the reaction between PbO and Nb2O5, which leads to secondary pyrochlore PbxNbyOz phases. Our method is based on the designed arrangement of particles of the starting compounds. The self‐assembly of the colloidal aggregates was governed by particle surface charge, which was adjusted by the suspension pH. At pH below 11.8 particle–particle interactions lead to close contacts between lead oxide and niobium oxide particles in the suspension as well as in the dried powders, whereas at pH above 11.8 close contacts between lead and niobium oxide particles are avoided. The suspensions of the starting powders were prepared at pH 10.0, 11.4, 12.5, and in acetone. After heating of the dried suspension with the pH set at 12.5 at 900°C, a pure perovskite PMN powder was obtained. On the contrary, the powders prepared from the pH 11.4, 10.0, and acetone suspensions still contained the detrimental pyrochlore phase after heating at 900°C. The properties of the ceramics prepared from the pH 12.5 suspension are superior in comparison with the other samples.

Mechanochemical Synthesis and Characteristics of Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>

This paper presents a novel mechanochemical synthesis technique for making nano-structured Pb(Mg1/3Nb2/3)O3 (PMN) ferroelectric material without annealing treatment in a much shorter time and at much lower temperature than those reported in the literature, by using the starting precursors MgO, PbO, and Nb2O5. Specimens of various milling time (3-6h) are characterized from XRD patterns to track and analyze the synthesizing procedure of this mechanochemical processing route. The time used to make the desired PMN powders varies with different milling power. When the constituent oxides were mechanically activated at 1.8KW milling power for 6h, the perovskite phase PMN powder was obtained; while it was formed when milling at 3KW for only 3h. Typical SEM images of the as-received PMN powders show that the powders are aggregated of nano-particles of about 100nm in size.

Effects of Silane Coupling Agent Treatment on Properties of PMN/EP Composites

The PMN/EP composites were prepared by resin casting method from PMN powder pretreated with silane coupling agent KH-550. The microstructure of the PMN/EP composite was observed by SEM, the damping property and dielectric property of the composite were investigated by dynamic mechanical analyzer and impedance analyzer respectively. In the composite prepared with PMN powder pretreated by 1.5% silane coupling agent, much epoxy resin fragment is attached in the surface of PMN particles. When the silane coupling agent concentration is 1.5%, the composite shows the best damping property. Dielectric analyses suggest that the dielectric constant of the PMN/EP composite decreases with the increase of silane coupling agent content, however the dielectric loss increases with the increase of silane coupling agent content.

Single‐Calcination Synthesis of Pyrochlore Free Pb(Mg1/3Nb2/3)O3 Powders Using Particle‐Coating Method

Using two‐step particle‐coating method, pyrochlore‐free Pb(Mg1/3Nb2/3)O3 (PMN) powders have been successfully synthesized by a single calcination step at a relatively lower calcined temperature of 850°C. The XRD and EDS results confirmed that the Mg–citric acid polymeric complex coatings effectively prevent direct contact between PbO and Nb2O5 and thus avoid the formation of pyrochlore phase. The coated powders were calcined directly without the ball‐milling procedure at 850°C. The pyrochlore‐free PMN powders obtained showed uniform and even grain size. The results showed that this method is an attractive method for the synthesis of PMN‐based composite powders.

PMN 계 유전체 적용 EL 소자의 광전특성 연구

In this study, the opto-electric properties of EL devices with PMN dielectric layer with variation of firing tempereature were investigated. For the PMN dielectric layer process, the paste was prepared by optimization of quantitative mixing of PMN powder, <TEX>$BaTiO_3$</TEX>, Glass Frit, <TEX>$\alpha$</TEX>-Terpineol and ethyl cellulose. The EL device stack consists of Alumina substrate (<TEX>$Al_2O_3$</TEX>), metallic electrode (Au), insulating layer (manufactured PMN paste), phosphor layer (ELPP- 030, ELK) and transparent electrode (ITO), which is well structure as a thick film EL device. The phase transformation properties of PMN dielectric with various firing temperatures of <TEX>$150^{\circ}C$</TEX> to <TEX>$850^{\circ}C$</TEX> was characterized by XRD. Also the opto-electric properties of EL devices with different firing temperature were investigated by LCR meter and spectrometer. We found the best opto-electric property was obtained at the condition of <TEX>$550^{\circ}C$</TEX> firing which is 3432.96 <TEX>$cd/m^2$</TEX> at 1948.3 pF Capacitance, 40 kHz Frequency, 40% Duty, Vth+330 V voltage.

Preparation and Characterization of Polyaniline/PMN Composite by &lt;i&gt;In Situ&lt;/i&gt; Polymerization Method

The PANI/PMN composite was prepared by one-step in-situ polymerization method and was characterized via FT-IR, XRD, SEM and TG. The results indicate that the best reaction conditions of in-situ polymerization are 0°C/24h.The PMN powder are entirely coated with PANI, when composite contains more than 60% PANI by volume. The steric hindrance effect of PMN powder decreases the crystallization degree of PANI which polymerizes on the surface of PMN powder in the process of in-situ polymerization. The main weight loss occurring between 300 and 480°C corresponds to the degradation of the PANI polymer chain.

DIELECTRIC PROPERTIES OF LEAD MAGNESIUM NIOBATE-LEAD TITANATE CERAMICS PREPARED BY MIXED-OXIDE METHOD

In this study, the (1-x) Pb ( Mg 1/3 Nb 2/3) O 3-x PbTiO 3 (when x=0.1, 0.3 and 0.5) ceramics were prepared from PMN and PT powders by a mixed-oxide method. The dielectric properties of the ceramics were measured as functions of both temperature (-150–400°C) and frequency (100 Hz–1 MHz). The results indicated that the dielectric properties of pseudo-cubic phase 0.9PMN-0.1PT and tetragonal phase 0.5PMN-0.5PT ceramics followed that of relaxor and normal ferroelectric behaviors, respectively, while the dielectric behaviors of a near MPB phase 0.7PMN-0.3PT ceramic showed a mixture of normal and relaxor ferroelectric behaviors. In addition, the Curie temperature (TC) increased with increasing PT contents, while the diffusivity decreased. This confirmed a gradual transition from a relaxor ferroelectric behavior in 0.9PMN-0.1PT to a normal ferroelectric behavior in 0.5PMN-0.5PT. The difference in dielectric behaviors was attributed to the structural symmetry of the ceramics.

Double Precursor Solution Coating Approach for Low‐Temperature Sintering of [Pb(Mg1/3Nb2/3)O3]0.63[PbTiO3]0.37 Solids

Lead‐based piezoelectric ceramics typically require sintering temperatures higher than 1000°C at which significant lead loss can occur. Here, we report a double precursor solution coating (PSC) method for fabricating low‐temperature sinterable polycrystalline [Pb(Mg1/3Nb2/3)O3]0.63‐[PbTiO3]0.37 (PMN–PT) ceramics. In this method, submicrometer crystalline PMN powder was first obtained by dispersing Mg(OH)2‐coated Nb2O5 particles in a lead acetate/ethylene glycol solution (first PSC), followed by calcination at 800°C. The crystalline PMN powder was subsequently suspended in a PT precursor solution containing lead acetate and titanium isopropoxide in ethylene glycol to form the PMN–PT precursor powder (second PSC) that could be sintered at a temperature as low as 900°C. The resultant d33 for samples sintered at 900°, 1000°, and 1100°C for 2 h were 600, 620, and 700 pm/V, respectively, comparable with the known value. We attributed the low sintering temperature to the reactive sintering nature of the present PMN–PT precursor powder. The reaction between the nanosize PT and the submicrometer‐size PMN occurred roughly in the same temperature range as the densification, 850°–900°C, thereby significantly accelerating the sintering process. The present PSC technique is very general and should be readily applicable to other multicomponent systems.

Effect of sintering conditions on the pyrochlore phase content in PMN–PFN ceramics prepared by sol–gel process

Lead magnesium niobate–lead iron niobate [(1 − x)Pb(Mg 1/3Nb 2/3)O 3– xPb(Fe 1/2Nb 1/2)O 3, (1 − x)PMN– xPFN] system, where x = 0.0–1.0, was prepared using sol–gel synthesis by mixing acetates Pb, Mg and Fe with Nb-ethylene glycol-tartarate complex at 80 °C. Single pyrochlore phase (Pb 1.83Mg 0.29Nb 1.71O 6.39 or Pb 3Nb 4O 13) was formed by the calcination of gels at 600 °C. Average particle sizes of pure PMN and PFN powders were ∼80 and 150 nm. The pyrochlore phases were partially decomposed to perovskite phase at sintering temperatures of 1150 and 1250 °C. The maximum bulk density in ceramic samples increased with both sintering temperature and the content of PFN phase in samples but despite these facts—the volume fractions of porosity were too high in all prepared samples. From the point of view of perovskite phase content, the optimum sintering temperature of PMN–PFN is shifted from 1200 to 1150 °C in comparison with the sample with PMN stoichiometry. Low values of ɛ r were measured in low density samples with high pyrochlore content and this characteristic is probably the main factor affecting ɛ r in prepared ceramics. In microstructures of PMN–PFN ceramics sintered at 1150 °C at different times, the bimodal grain size distribution was observed with small grains of globular shape and larger grains of regular or octahedral shape. The results of EDX and XRD analysis showed that the more complex types of pyrochlore phases were present in ceramics.

Phase formation and microstructure of Nd+3 doped Pb(Mg1/3Nb2/3)O3 prepared by sol–gel method

The aim of this study was to investigate the effects of the rare earth element neodymium on the phase formation and microstructural development of relaxor ferroelectric lead magnesium niobate, Pb(Mg1/3Nb2/3)O3 (PMN) system. Perovskite phase PMN powders were prepared using the sol–gel method and the effect of neodymium doping was investigated at different doping levels ranging from 0.1 mol% to 30 mol%. The precursors employed in the sol–gel process were lead (II) acetate, magnesium ethoxide, and niobium (V) ethoxide. All the experiments were performed at room temperature while the calcination temperatures ranged between 800 °C and 1,100 °C. Results showed that it was possible to obtain the pure perovskite phase at 950 °C using the sol–gel method. Nd+3 addition influenced the phase formation and microstructure of the multicomponent system. Pyrochlore was detected along with the perovskite phase above 10 mol% Nd. Results also demonstrated that grain size of the synthesized powders depended on the Nd+3 concentration.

Preparations and Characterizations of Perovskite PMN Ceramics by Using a One-Step Calcination Method

A relaxor ferroelectric material, Pb(Mg1/3Nb2/3)O3 (PMN) powder with a pyrochlore-free phase, was prepared by using a one-step calcinations method. The pyrochlore phase was prevented by coating Mg(OH)2 on Nb2O5 particles. Pure-perovskite PMN powder was synthesized by a single calcination of the coating powder mixed with appropriate amounts of PbO at 900 oC for 2 h. The pyrochlore-free perovskite PMN powders were sintered to 96.9% density at 1100 oC. The sintered PMN ceramics exhibited a dielectric constant maximum of ~11 700 at room temperature at a frequency of 1 kHz.

Effect of milling time on the properties of Pb(Mg1/3Nb2/3)O3 ceramics using the starting precursors PbO and MgNb2O6

Abstract Lead magnesium niobate, Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) ceramics were prepared from the columbite method using calcined powders of various milling time (24–96 h). The effects on the grain size and dielectric properties of the ceramics were investigated. The results show that dielectric properties of ceramics are strongly influenced by the milling time of the starting precursors. Higher percentage of perovskite phase was found in the ceramics that was milled longer and thus the dielectric constant was found to increase when compared to the conventional 24 h milled results. Moreover, milling time also affected the particle size of the starting precursors and that of PMN powders. Therefore, milling time did not only affect the particle size of PMN powders but also the resultant grain size and the formation of perovskite phase, consequently affecting the dielectric constant of the ceramics.

Effects of magnesium niobate precursor and calcination condition on phase formation and morphology of lead magnesium niobate powders

A perovskite phase of lead magnesium niobate, Pb(Mg 1/3Nb 2/3)O 3 or PMN, powders has been synthesized by a rapid vibro-milling technique. Both columbite MgNb 2O 6 and corundum Mg 4Nb 2O 9 have been employed as magnesium niobate precursors, with the formation of the PMN phase investigated as a function of calcination conditions by thermal gravimetric and differential thermal analysis (TG–DTA) and X-ray diffraction (XRD). The particle size distribution of the calcined powders was determined by laser diffraction technique. Morphology, crystal structure and phase composition have been determined via a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) techniques. The magnesium niobate precursor and calcination condition have been found to have a pronounced effect on the phase and morphology evolution of the calcined PMN powders. It is seen that optimisation of calcination conditions can lead to a single-phase PMN in both methods. However, the formation temperature and dwell time for single-phase PMN powders were lower for the synthetic method employing a columbite MgNb 2O 6 precursor.

Study of k and LiNbO&lt;sub&gt;3&lt;/sub&gt; addition on the final properties of the relaxor pmn processed by powder blend

PMN ceramic relaxor has been investigated by several researchers and many aspects of this material, like powder morphology, phase decomposition, weight loss during sintering process, densification, between others, still are investigated. PMN powder preparation has been shown more efficient when synthesized by columbite route, however lead addition stage for the PMN powder synthesis remains problematical. Therefore, this work proposes a new association of methodologies, using columbite route and the hydroxide precipitation method. Through use of the powder mixture technique, which permitted to obtain good green and sintered densities, was possible to observe K + y Li + dopants reduce weight loss in sintering process and change significantly the dielectric properties. Addition of LiNbO 3 seeds in conformation stage, which react in a distinct way as a function of the particle size, promotes the formation of differenced grains in the ceramic bulk. Consequently, very different dielectrics properties from conventional PMN ceramic were obtained.

Effect of PbO excess on the formation of lead magnesium niobate perovskite by the columbite method

The effect of lead excess on the pyrochlore-type formation in Pb(Mg 1/3Nb 2/3)O 3 (PMN) powders has been investigated. The polymeric precursor method was used in the synthesis of the columbite in association to the partial oxalate method to synthesize the PMN powder samples. Structure refinement of the columbite precursor and PMN powders was carried out using the Rietveld method. The quantitative phase analysis showed that the amount of perovskite phase is not affected by PbO excess, but a great excess drives the pyrochlore-type formation so that 3 wt.% of PbO causes the predominance of Mg-containing pyrochlore phase. Using the refined data obtained from the Rietveld refinement, the compositional fluctuation in the perovskite phase was calculated from Nb/Mg ratio values and Pb occupation factor. Mg inclusion occurs concomitant with Pb one into PMN perovskite phase and this effect is directed by PbO excess during powder synthesis.

Single‐Calcination Synthesis of Pyrochlore‐Free 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 and Pb(Mg1/3Nb2/3)O3 Ceramics Using a Coating Method

A coating approach for synthesizing 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (0.9PMN–0.1PT) and PMN using a single calcination step was demonstrated. The pyrochlore phase was prevented by coating Mg(OH)2 on Nb2O5 particles. Coating of Mg(OH)2 on Nb2O5 was done by precipitating Mg(OH)2 in an aqueous Nb2O5 suspension at pH 10. The coating was confirmed using optical micrographs and zeta‐potential measurements. A single calcination treatment of the Mg(OH)2‐coated Nb2O5 particles mixed with appropriate amounts of PbO and PbTiO3 powders at 900°C for 2 h produced pyrochlore‐free perovskite 0.9PMN–0.1PT and PMN powders. The elimination of the pyrochlore phase was attributed to the separation of PbO and Nb2O5 by the Mg(OH)2 coating. The Mg(OH)2 coating on the Nb2O5 improved the mixing of Mg(OH)2 and Nb2O5 and decreased the temperature for complete columbite conversion to ∼850°C. The pyrochlore‐free perovskite 0.9PMN–0.1PT powders were sintered to 97% density at 1150°C. The sintered 0.9PMN–0.1PT ceramics exhibited a dielectric constant maximum of ∼24 660 at 45°C at a frequency of 1 kHz.

The Influence of the Sintering System on PMN Properties

PMN powder samples with PbO excess of 0, 1, 2 and 3% were submitted to the pressing and sintering at 1200°C for 4h with a heating rate of 3°C/min. A new sintering system, developed at our laboratories, was used. It allows obtaining more information on the sintering process. The sintered samples in the new system were compared to sintered samples in the C system. The microstructure, dielectric properties and the effect of the PbO excess in different sintering systems were compared. The N system permitted to obtain a ceramic with better properties, such density, dielectric constant and very homogeneous microstructure.

Effect of the Addition of Potassium or Lithium on the Columbite Precursor Microstructure

Pechini method has been used to synthesize MN powders with stoichiometric control. By this method, K and Li-doped MN in the range from 0.1 to 5.0 mol% of dopants have been obtained at relatively lower temperatures than it is possible with the conventional mixture of oxides. The results from BET analysis indicated that the doped powders have lower surface area and the attrition milling promotes an increase in surface area values for all powders. Rietveld method was used to calculate the mean crystallite size and the microstrain in the crystal. With additions of up to 5.0 mol% of K or 2.0 mol% of Li, it is possible to obtain MN as a solid solution. Both dopants change the cell parameters of the columbite phase crystal, reduce the microstrain, and increase the main crystallite size. The analysis of results from SEM indicates that powders prepared with addition of dopants are more agglomerate than pure PMN powder.