Polymorphism of bismuth sesquioxide. II. Effect of oxide additions on the polymorphism of Bi2O3

Levin, Ernest M.; Roth, Robert

doi:10.6028/jres.068a.020

Cited by 285 publications

(140 citation statements)

References 10 publications

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“…It seems that quenching cannot prevent a change in crystal symmetry of Cu x Mn 3-x O 4 spinel, and is not a reliable way to determine equilibrium structure in this system. Over 40 years ago, Levin and Roth found that the high-temperature phases in the bismuth oxide system detected by high-temperature XRD were different from those measured in the cooled samples, and concluded that in situ studies of high-temperature phases were necessary for studying that system [30]. Clearly, the same conclusion applies to Cu-Mn-O system.…”

Section: In Situ High-temperature Neutron Diffraction Measurementsmentioning

confidence: 97%

In situ high-temperature X-ray and neutron diffraction of Cu–Mn oxide phases

et al. 2010

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Copper-manganese oxides were analyzed by in situ high-temperature powder neutron and X-ray diffraction to investigate their crystal structure. Cu-Mn spinel was found to form a continuous solid solution with cubic symmetry between Mn 3 O 4 and Cu 2 MnO 4 . A high-temperature phase with approximate composition Cu 5 Mn 4 O 9 was shown to have hexagonal symmetry. The cation distribution and lattice parameters of Cu-Mn spinel were resolved through Rietveld refinement of in situ neutron diffraction data. The results demonstrated that the Cu ion has a lower octahedral site preference than manganese ions, and quenching is not a reliable method to determine the equilibrium structure in the system.

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Section: In Situ High-temperature Neutron Diffraction Measurementsmentioning

confidence: 97%

In situ high-temperature X-ray and neutron diffraction of Cu–Mn oxide phases

et al. 2010

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“…Levin y Roth [1] en su estudio destacan la presencia de un eutectico a 740ºC, así como la presencia de la fase estable 6Bi 2 O 3 ·ZnO molar, de fusión congruente.…”

Section: Introductionunclassified

Estudio de la región rica en Bi2O3 en el sistema binario ZnO-Bi2O3

Rubia¹,

Peiteado²,

Fernández³

et al. 2004

Bol. Soc. Esp. Ceram. Vidr.

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Los materiales cerámicos basados en el sistema binario ZnO-Bi 2 O 3 tienen su principal aplicación en el campo de los varistores. El sistema binario ZnO-Bi 2 O 3 resulta especialmente relevante para la formación de la microestructura funcional de varistores. La determinación de las diferentes fases en equilibrio a alta temperatura en la región rica en Bi 2 O 3 en el sistema binario ZnO-Bi 2 O 3 permitirá interpretar correctamente el desarrollo microestructural. El estudio de las fases en equilibrio se ha llevado a cabo mediante difracción de rayos X, microscopía electrónica de barrido (MEB) y análisis térmico diferencial (ATD). Tratamientos a diferentes temperaturas, en la zona rica en Bi 2 O 3 del sistema, han permitido determinar la presencia del compuesto 19Bi 2 O 3 ·ZnO como fase estable en equilibrio, en lugar del compuesto 24Bi 2 O 3 ·ZnO. Palabras clave: diagrama de fases, varistores, microestructuraStudy at the Bi 2 O 3 -rich region of the ZnO-Bi 2 O 3 system Ceramic materials based in the ZnO-Bi 2 O 3 system have their principal application as varistors. The binary system ZnO-Bi 2 O 3 is specially relevant to the formation of the microstructure responsable of the varistor behaviour. The study of the different equilibrium phases at high temperatures at the Bi 2 O 3 -rich region of the ZnO-Bi 2 O 3 will allow a correct understanding of the microstructural development. Equilibrium phases have been analyzed by XRD, SEM and DTA. Different temperature treatments of samples formulated in the Bi 2 O 3 rich region of the ZnO-Bi 2 O 3 binary system have allowed to determine the phase 19Bi 2 O 3 ·ZnO as the equilibrium one instead of the 24Bi 2 O 3 ·ZnO phase. Keywords: phases diagrams, varistors, microstructure INTRODUCCIÓNLos materiales cerámicos multicomponentes basados en ZnO dopados con pequeñas cantidades de Bi 2 O 3 muestran un alto grado de no linealidad en su respuesta eléctrica corriente-voltaje. Este comportamiento no óhmico es consecuencia de la microestructura, donde granos de ZnO semiconductores están separados por una fase intergranular rica en Bi 2 O 3 dando lugar a la formación de barreras de potencial.La importancia del diagrama de fases ZnO-Bi 2 O 3 para el procesamiento de materiales varistores es consecuencia de la baja temperatura del eutéctico así como la baja solubilidad del Bi 2 O 3 en ZnO. Dicho diagrama continua siendo objeto de estudio y existen en la literatura fuertes discrepancias en cuanto a fases en equilibrio así como la presencia de fases metaestables, como se refleja en la bibliografía.Levin y Roth [1] en su estudio destacan la presencia de un eutectico a 740ºC, así como la presencia de la fase estable 6Bi 2 O 3 ·ZnO molar, de fusión congruente.Posteriormente Safronov et al [2] mediante estudios de ATD y DRX confirmó la presencia del eutectico a 740ºC para una composición: 86% moles de Bi 2 O 3 -14% moles de ZnO (6.14Bi 2 O 3 ·ZnO) y la transformación de fase de α-Bi 2 O 3 a δ-Bi 2 O 3 a 735ºC, así como la presencia de la fase 24Bi 2 O 3 ·ZnO (Bi 48 ZnO 73 ), que funde incongrue...

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“…Bi203 easily forms a bcc structure if it is contaminated by A1, Si, Fe, Zr, Ce, T1 and Pb as reported by Aurivillius and Sill6n [15] and other authors [16,17]. This b.c.c, structure may be t The detection limit of Zr in a Bi203-rich phase is about 3%.…”

Section: Methodsmentioning

confidence: 61%

Free energy of formation of stabilized Bi2O3 (fcc) from e.m.f. measurements

Verkerk

Burggraaf

1980

J Appl Electrochem

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Using cells with calcia stabilized zirconia as the solid electrolyte, the standard free energy of formation of stabilized Bi203 (fcc) was determined in the temperature range 750-950 K. The stability against reduction of stabilized Bi:O3 (fcc) is not increased with respect to pure 6-Bi203 (fcc). The corrosion of the calcia stabilized zirconia tube caused by Bi203 which took place along the grain boundaries, was investigated.

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Polymorphism of bismuth sesquioxide. II. Effect of oxide additions on the polymorphism of Bi2O3

Cited by 285 publications

References 10 publications

In situ high-temperature X-ray and neutron diffraction of Cu–Mn oxide phases

In situ high-temperature X-ray and neutron diffraction of Cu–Mn oxide phases

Estudio de la región rica en Bi<sub>2</sub>O<sub>3</sub> en el sistema binario ZnO-Bi<sub>2</sub>O<sub>3</sub>

Free energy of formation of stabilized Bi2O3 (fcc) from e.m.f. measurements

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