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

Cavalheiro, Alberto Adriano; Zaghete, M. A.; Paiva‐Santos, C. O.; Varela, José Arana

doi:10.1590/s1516-14392002000400002

Cited by 4 publications

(5 citation statements)

References 14 publications

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“…However, when 2mol% of Li is added, there is an appearance of an extra peak that is associated to another precipitated phase, probably rich in lithium. This effect is not related to titanium presence at the precursor since it could be verified when high concentration of Li was added in no-modified MN precursor [15]. Calculus of cell parameters in MN T powders was performed using the Rietveld method.…”

Section: Resultsmentioning

confidence: 96%

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Synthesis and Characterization of 0.9PMN-0.1PT Powders by the Use of a Modified Columbite Precursor

Bruno

Cavalheiro

Zaghete

et al. 2005

MSF

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The complex perovskite compound 0.9PbMg1/3Nb2/3O3-0.1PbTiO3 is one of the most promising relaxor ceramic because the addition of lead titanate increases Tm by about 5°C/mol% from intrinsic Tm value for pure PMN (near –7 to -15°C). A Ti-modified columbite precursor was used to prepare PMN-PT powders containing single perovskite phase. This variation on columbite route includes Ti insertion in MgNb2O6 orthorhombic structure so that individual PT synthesis becomes unnecessary. Furthermore, effects of Li additive on columbite and PMN-PT structures were studied by XRD to verify the phase formation at each processing step. XRD data were also used for the structural refinement by Rietveld method. The additive acts increasing columbite powders crystallinity, and the amount of perovskite phase was insignificantly decreased by lithium addition. By SEM micrographs it was observed that Li presence in PMN-PT powders leads to the formation of rounded primary particles and for 1mol% of additive, the grain size is not changed, different from when this concentration is enhanced to 2mol%.

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Section: Resultsmentioning

confidence: 96%

“…This additive showed many potentialities in PMN ceramic for favoring the perovskite phase formation, reducing weight loss on sintering process and displacing T m to higher temperature. This additive also increases lattice parameters and the crystallinity of MN precursor when the columbite route is used to synthesize PMN powders [15,16].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of 0.9PMN-0.1PT Powders by the Use of a Modified Columbite Precursor

Bruno

Cavalheiro

Zaghete

et al. 2005

MSF

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show abstract

“…Esto es debido al hecho de que el parámetro de red es afectado para pequeñas concentraciones de dopantes, pero la contribución en el peso molecular solamente ocurre para concentraciones más elevadas. Los difractogramas de rayos X no presentaran diferencias en forma o posición de los picos, correspondiendo a patrones ya descritos en la literatura (19,20) y por esto no son aquí presentados.…”

Section: Métodos De Caracterizaciónunclassified

“…En este contexto, se han estudiado los dopantes KNbO 3 y LiNbO 3 añadidos en el precursor columbita, donde se han observado influencias de la cristalización y cambios en el parámetro de red. Estos dopantes han sido introducidos por primera vez buscando efectos o mejorías en las propiedades del PMN basados en la correlación que hay con BaTiO 3 y PbTiO 3 , que han sido de gran uso en este material (19)(20).…”

Section: Introductionunclassified

Estudio de PMN cerámico dopado con KNbO<sub>3</sub> y LiNbO<sub>3</sub> sintetizado por Pechini

Cavalheiro¹,

Zaghete²,

Paiva‐Santos³

et al. 2002

Bol. Soc. Esp. Ceram. Vidr.

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El PMN pertenece a una clase especial de materiales conocido como ferroeléctricos relaxores. Posee gran eficacia volumétri-ca debido a su gran constante dieléctrica, siendo un perfecto candidato para la aplicación en capacitores multicapas. Su preparación es más ventajosa cuando se sintetiza por la ruta de la columbita. Las preparaciones de la columbita y del PMN se basaron en los métodos Pechini y Oxalato Parcial, respectivamente. Se ha estudiado los efectos de los dopantes KNbO 3 y LiNbO 3 añadidos a varias concentraciones. La idea esta basada en las correlaciones que estos tienen con BaTiO 3 y PbTiO 3 , respectivamente. El proceso entero se caracterizó mediante ATD/TG, DRX, MEB y determinación de la superficie específica de los polvos. El dopante LiNbO 3 promueve la pre-sinterización de las partículas de MN, reduciendo la superficie específica del polvo. No hay crecimiento de partícula, pero ocurre su alargamiento. En cambio, para el KNbO 3 ocurre crecimiento de partícula, pero los aglomerados son más blandos. El efecto causado por los dopantes durante la síntesis de los polvos de PMN es diferente a los producidos en el precursor. El precursor puro presenta tamaño medio de partícula de 0,2µm, pero la adición de 5,0%molar de dopante produce la formación de aglomerados de ~4µm. La adición de LiNbO 3 produce partículas arredondeadas y pre-sinterización, mientras la adición de KNbO 3 no altera la forma de las partículas. Palabras clave: Ferroeléctrico, Relaxor, PMN, Columbita, Pechini. Study of KNbO 3 and LiNbO 3 -doped ceramic PMN synthesized by PechiniPMN belongs to a special class of materials named relaxor ferroelectrics. It has high volumetric efficiency due to its high dielectric constant, which makes it in a perfect material for application in multilayer capacitors. When prepared the columbite route its preparation has many advantages. In this work, the preparations of columbite and PMN were done by Pechini and Partial Oxalate methods, respectively. The effects of the KNbO 3 and LiNbO 3 dopants added in various concentrations. The idea is founded on the correlations that they have with BaTiO 3 y PbTiO 3 , respectively. The whole process was supervised by TG/DTA, XRD, SEM and determination of the specific surface area of the powders. LiNbO 3 carries out the pre-sinterization of the particles, observed by a reduction in the surface area. There are not particle grow, but occur its lengthening. However, for KNbO 3 these particle growth, but the agglomerates are softer. The effect produced by the doping during the synthesis of the PMN powder is different from the one produced in the columbite precursor. Pure precursor shows an average particle size of 0,2µm, but the addition of 5,0mol% of dopants carries out the formation of agglomerates close to 4µm. LiNbO 3 addition carries out spherical particles and pre-sinterization, while KNbO 3 addition does not change the particles shape.

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“…This additive showed many potentialities in this ceramic for reducing weight loss in the sintering process and displacing T m to higher temperature. This additive also increases the MN precursor crystallinity when the columbite route is used [8,9].…”

Section: Introductionmentioning

confidence: 99%

Study of Ti-Modified Columbite Route and the Effect of Lithium Doping in 0.9PMN-0.1PT Ceramics

et al. 2006

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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.

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

Cited by 4 publications

References 14 publications

Synthesis and Characterization of 0.9PMN-0.1PT Powders by the Use of a Modified Columbite Precursor

Synthesis and Characterization of 0.9PMN-0.1PT Powders by the Use of a Modified Columbite Precursor

Estudio de PMN cerámico dopado con KNbO<sub>3</sub> y LiNbO<sub>3</sub> sintetizado por Pechini

Study of Ti-Modified Columbite Route and the Effect of Lithium Doping in 0.9PMN-0.1PT Ceramics

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