Microstructural Development in SnO2‐Doped ZnO–Bi2O3 Ceramics

Daneu, Nina; Rečnik, Aleksander; Bernik, Slavko; Kolář, D.

doi:10.1111/j.1151-2916.2000.tb01699.x

Cited by 61 publications

(78 citation statements)

References 21 publications

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“…In order to more efficiently control the ZnO grain size, other dopants are added to the binary ZnO-Bi 2 O 3 varistor composition. The most common grain growth controlling additives for ZnO-based varistor ceramics are Sb 2 O 3 , SnO 2 and TiO 2 [4][5][6][7][8]. Empirically, Sb 2 O 3 would be added when small ZnO grain size is desired, while the addition of TiO 2 generally results in large-grained microstructure.…”

Section: The Role Of Dopants In Zno-based Varistor Ceramicsmentioning

confidence: 99%

“…To understand the role of grain growth modifying additives in the ZnO grain growth, basic ZnO-Bi 2 O 3 varistor composition was doped with SnO 2 [8]. While the addition of SnO 2 to varistor ceramics is not favourable for the electric properties of the ZnO-based varistor, because it increases the leakage current [15], it turned out to be a perfect dopant for the grain growth mechanisms studies.…”

Section: Microstructure Development In Sno 2 -Doped Zno-bi 2 O 3 Ceramentioning

confidence: 99%

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Inversion boundary induced grain growth in ZnO ceramics: from atomic-scale investigations to microstructural engineering

Daneu¹,

Bernik

Rečnik

2011

J. Phys.: Conf. Ser.

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Abstract. In semiconducting materials special boundaries play the key role in crystal growth. They introduce an abrupt structural and chemical anisotropy, which is readily reflected in an unusual microstructure evolution, whereas their local structure affects the physical properties of semiconducting materials. These effects, however, can be exploited to tailor the electronic and optical properties of the materials, as demonstrated in this review. The presented topic fits in the field of preparatory stage of phase transformations, manifested through evolution of chemically induced structural faults. In the noncentrosymmetric structure of ZnO, inversion boundaries (IBs) are the most common type of planar faults that can be triggered by the addition of specific spinel-forming dopants (Sb 2 O 3 , SnO 2 , TiO 2 ). In addition to conventional HRTEM techniques several new methods were developed to resolve crystallography and atomic-scale chemistry of IBs. The absolute orientation of the polar c-axes on both sides of the IB was determined by a novel quantitative microdiffraction method, providing a reliable identification of crystal polarity in noncentrosymmetric crystals. To determine sub-monolayer quantities of dopants on the IB, we developed a special technique of analytical electron microscopy using concentric electron probe (CEP) in EDS or EELS mode, providing more accurate and precise results than any other available technique. Knowing the local crystal chemistry of IBs we were able to design experiments to identify their formation mechanism. IBs nucleate in the early stage of grain growth as a dopant-rich topotaxial 2D reaction product on Zn-terminated surfaces of ZnO grains. Soon after their nucleation, ZnO is epitaxially grown on the inherent 2D phase in an inverted orientation, which effectively starts to dictate anisotropic growth of the infected crystallite. In very short time the grains with IBs dominate the entire microstructure in ZnO ceramics via IB-induced exaggerated grain growth mechanism. This phenomenon was used to design physical properties of ZnO-based varistor ceramics, whereas the bottom-up approach demonstrated here provides the basic tool for microstructural engineering of functional materials in virtually any system that is prone to formation of special boundaries.

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Section: The Role Of Dopants In Zno-based Varistor Ceramicsmentioning

confidence: 99%

Section: Microstructure Development In Sno 2 -Doped Zno-bi 2 O 3 Ceramentioning

confidence: 99%

Inversion boundary induced grain growth in ZnO ceramics: from atomic-scale investigations to microstructural engineering

Daneu¹,

Bernik

Rečnik

2011

J. Phys.: Conf. Ser.

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“…El desarrollo de las uniones nanométricas ZnOBi 2 O 3 -ZnO eléctricamente activas, tiene lugar durante el proceso de sinterización, en el que la formación de fases secundarias y los procesos de difusión en estado sólido y líquido juegan un papel crítico (3,6). En el inicio de la sinterización, llevada a cabo en atmósfera de aire, se forma una fase intermedia con estructura tipo pirocloro, Bi 2 (Zn 4/3 Sb 2/3 )O 6 , que a temperaturas más elevadas se transforma en la fase espinela Zn 7 Sb 2 O 12 , por medio de reacciones que dependen de la relación Bi/Sb, y que se ven modificadas por la presencia de los otros óxidos minoritarios (7,8 (9,10,11). Cuando es preciso un control muy estricto del tamaño de grano final del material, es necesario recurrir a un doble tratamiento térmico con el objeto de formar primero la fase espinela y proceder a la sinterización después, garantizando de este modo la presencia de espinela desde el inicio de la sinterización y un mejor control en el crecimiento de grano (1,12).…”

Section: Introduccionunclassified

Incorporación de la fase Zn7Sb2O12 previamente sintetizada en varistores cerámicos basados en ZnO

Peiteado¹,

Fernández²,

Caballero³

2002

Bol. Soc. Esp. Ceram. Vidr.

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Una de las reacciones que tiene lugar durante la sinterización de varistores cerámicos basados en el sistema ZnO-Bi 2 O 3 -Sb 2 O 3 es la formación de la fase Zn 7 Sb 2 O 12 , de estructura tipo espinela, que ocurre en el intervalo de temperaturas comprendido entre 900 y 1100ºC, dependiendo de la composición específica del material. Esta fase es la responsable del control del crecimiento de grano y su distribución en el seno del material como una segunda fase dispersa en la matriz mayoritaria de granos de ZnO determinará la cinética del crecimiento de los granos. Sin embargo, el proceso de nucleación y crecimiento de esta fase resulta difícil de controlar cuantitativamente, aspecto que se refleja en las características finales del dispositivo varistor obtenido. En el presente trabajo se analiza el efecto de la incorporación de la fase espinela previamente sintetizada a partir de los óxidos de zinc y antimonio. El análisis mediante Microscopía Electrónica de Barrido (MEB) de la microestructura de muestras sinterizadas a diferentes temperaturas, revela un mayor control microestructural en los materiales en los que se ha incorporado la espinela sintetizada. La respuesta Intensidad-Voltaje de estos materiales es coherente con las característi-cas microestructurales obtenidas, observándose una mayor reproducibilidad en el material. Palabras clave: varistor, microestructura, espinela, bordes de grano. Incorporation of Zn 7 Sb 2 O 12 spinel phase previously synthesized on ZnO ceramic varistors.During the sintering process of ZnO-Bi 2 O 3 -Sb 2 O 3 based varistors, different reactions take place. The formation of the Zn 7 Sb 2 O 12 spinel phase occurs between 900 and 1100ºC depending on the composition of the material. The spinel phase acts as ZnO grain growth inhibitor and its distribution on the whole material as a secondary phase in the matrix of ZnO grains determines the kinetics of grain growth. However, it is difficult to control the nucleation and growth of this phase, and this concerns on the final grain size and consequently on the characteristics of the varistor device. The present study has focused on the incorporation of the previously synthesized spinel phase. Scanning Electronic Microscopy analysis of sintered samples reveals a better control of microstructure in those materials with the synthesized spinel phase. The electrical behaviour of these materials agrees with the microstructural features and a greater reproducibility is observed. Key words: varistor, microstructure, spinel, grain boundary INTRODUCCIONLos varistores cerámicos basados en óxido de zinc son sistemas multicomponente caracterizados por un comportamiento eléctrico intensidad-voltaje no lineal, que se emplean como dispositivos protectores frente a sobretensiones transitorias y estabilizadores de voltaje en circuitos electrónicos (1,2,3). El material está constituido principalmente por ZnO con pequeñas cantidades de dopantes tales como Bi 2 O 3 , Sb 2 O 3 , CoO, MnO 2 y Cr 2 O 3 . El comportamiento no óhmico de un varistor es función de su...

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“…Cross sections of the samples were mechanically ground and polished, followed by etching in dilute hydrochloric acid. 13,14) We examined the noise reduction effect by repeated observations. Figure 3 shows an example of the repeated observations, indicating that the noise appearing in the dark region is significantly suppressed and the contract is enhanced with accumulation.…”

Section: Some CL Observationsmentioning

confidence: 99%

Ultra-Fast Spectrometric Cathodoluminescence Scanning Microscopy for Materials Analysis

Saijo

Shiojiri

2010

Mater. Trans.

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We have constructed a cathodoluminescence (CL) detection system that records the CL spectra emitted from each point raster-scanned by the incident electron probe in a conventional scanning electron microscope. The CL spectrum is detected by a 32 channel high-speed highsensitive photoelectron multiplier array set behind the spectrometer. The shortest signal sampling time is 8 s for a frame of 512Â512 pixels and all the imaging and spectroscopic signals are stored in two 8-megabyte files. Maximum image size is 2048Â2048 pixels. The microscope displays a spectral accurate full color (whole spectrum) CL image, twenty-nine monochromic images and the spectrum of each pixel point in the corresponding secondary electron image. The spatial resolution of CL image reaches 25 nm by reducing the quantum noise and the phosphorescent delay effect using a slow signal sampling time of 40 s with a 6-keV incident electron probe. Some examples are demonstrated using SnO 2 -doped ZnO-Ba 2 O 3 ceramics and photosensitive cyanine dyes.

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Microstructural Development in SnO₂‐Doped ZnO–Bi₂O₃ Ceramics

Cited by 61 publications

References 21 publications

Inversion boundary induced grain growth in ZnO ceramics: from atomic-scale investigations to microstructural engineering

Inversion boundary induced grain growth in ZnO ceramics: from atomic-scale investigations to microstructural engineering

Incorporación de la fase Zn<sub>7</sub>Sb<sub>2</sub>O<sub>12</sub> previamente sintetizada en varistores cerámicos basados en ZnO

Ultra-Fast Spectrometric Cathodoluminescence Scanning Microscopy for Materials Analysis

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