Recent research developments in SnO2-based varistors

Cassia-Santos, M. R.; Sousa, Vânia Caldas de; Oliveira, Marcelo Moizinho; Sensato, Fabrício R.; Bacelar, W. K.; Gomes, J. W.; Longo, Elson; Leite, E. R.; Varela, José Arana

doi:10.1016/j.matchemphys.2003.12.014

Cited by 77 publications

(25 citation statements)

References 52 publications

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“…Moreover, the optical, electronic and catalytic properties of SnO 2 depend critically on surface modifications such as impurities, defects or adsorbate [13][14][15][16], and especially, its electric conductivity varies sensitively upon adsorption of gas molecule at the surface [17][18][19]. Such conductance change of the sensing layer was well established to be the basic detection principle of the chemical gas sensor, and yet a fundamental understanding of the key phenomena at the SnO 2 surface remains debatable [20][21][22][23][24]. This gap in our understanding is also a problem for tailoring efficient gas sensors based on SnO 2 with desirable sensing characteristics, such as high sensitivity and selectivity, long-term stability, and fast response time.…”

Section: Introductionmentioning

confidence: 99%

Ab initio thermodynamic study of the SnO₂(110) surface in an O₂ and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO₂

Hong

Kye

et al. 2016

Phys. Chem. Chem. Phys.

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For the purpose of elucidating the gas sensing mechanism of SnO 2 for NO and NO 2 gases, we calculate the phase diagram of SnO 2 (110) surface in contact with an O 2 and NO gas environment by means of ab initio thermodynamic method. Firstly we build a range of surface slab models of oxygen pre-adsorbed SnO 2 (110) surfaces using (1×1) and (2×1) surface unit cells and calculate their Gibbs free energies considering only oxygen chemical potential. The fully reduced surface containing the bridging and in-plane oxygen vacancies in the oxygen-poor condition, while the fully oxidized surface containing the bridging oxygen and oxygen dimer in the oxygen-rich condition, and the stoichiometric surface in between, were proved to be most stable. Using the selected plausible NO-adsorbed surfaces, we then determine the surface phase diagram of SnO 2 (110) surfaces in (∆µ O , ∆µ NO ) space. In the NO-rich condition, the most stable surfaces were those formed by NO adsorption on the most stable surfaces in contact with only oxygen gas. Through the analysis of electronic charge transferring and density of states during NO x adsorption on the surface, we provide a meaningful understanding about the gas sensing mechanism.

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Section: Introductionmentioning

confidence: 99%

Ab initio thermodynamic study of the SnO₂(110) surface in an O₂ and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO₂

Hong

Kye

et al. 2016

Phys. Chem. Chem. Phys.

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“…Assuming Schottky-type voltage barriers at grain-grain interfaces, the negative surface charge at the interface is compensated by the positive charge in the depletion layers at both sides of the grain boundary [7]. This atomic defects model involves positively charged donors (V O , V O , Nb Sn ) located in the depletion layers and negatively charged acceptors (Fe Sn 00 , Fe Sn 000 , Co Sn 000 , Co Sn 00 , V Sn 0000 , V Sn 00 , O 0 , O 00 ) at grain-grain interfaces that contribute to the formation of a potential barrier [7,9,13]. Then, the increased nonlinearity and higher E r for iron-doped samples could be attributed to the segregation of iron to the grain boundary regions.…”

Section: Microstructural Properties Of Sintered Samplesmentioning

confidence: 99%

“…As well, the microstructure and electrical response of dense SnO 2 -based ceramics have been exhaustively studied since their nonlinear electrical behavior was reported for the first time [4]. Oxides such as CuO [5], MnO 2 [5][6][7], Co 2 O 3 [8], Co 3 O 4 [5,9,10], ZnO, CaCO 3 [10], CoO [4,6,7,11] and CaO are used as sintering aids whereas Nb 2 O 5 [4,7,9], Ta 2 O 5 [8], V 2 O 5 [12], Sb 2 O 3 [5,10], La 2 O 3 [7], Fe 2 O 3 [9,13], BaCO 3 [14] and Cr 2 O 3 [7,15,16], and have been found to control the electrical conductivity of sintered samples.…”

Section: Introductionmentioning

confidence: 99%

From tin oxalate to (Fe, Co, Nb)-doped SnO2: Sintering behavior, microstructural and electrical features

Parra

Ramajo

Góes

et al. 2008

Materials Research Bulletin

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Highly reactive SnO 2 -doped nanocrystalline powders with average particle size of 20 nm and specific surface areas above 30 m 2 / g were obtained through the polymeric precursor method with tin oxalate (SnC 2 O 4 ) as a chloride-free precursor for SnO 2 . Powders and sintered discs were characterized by means of X-ray powder diffraction (XRD), SEM and TEM. The influence of Co and Fe on the microstructure development and on the electrical properties of dense SnO 2 -based ceramics was studied. Co and Fe species were found to decrease in more than 70 8C the sintering temperature of SnO 2 with respect to mixed oxide procedures. Secondary phases enriched in Co and Fe were detected and identified in sintered samples with XRD. Current-voltage curves were registered for electrical characterization. Doping with iron increased the electrical breakdown field and a nonlinearity coefficient of 20 was achieved. #

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“…Por ejemplo se ha trabajado con varistores basados en TiO 2 , en los cuales iones divalentes tales como bario y calcio desempeñan el papel del bismuto (varistor forming dopant) e iones pentavalentes como tántalo o niobio contribuyen a incrementar la no-linealidad del dispositivo (84). También se ha encontrado comportamiento varistor en materiales basados en BaTiO 3 , SrTiO 3 , o incluso en WO 3 (85,86), pero sin duda los mejores resultados se han encontrado con los varistores basados en SnO 2 (87). El óxido de estaño es un semiconductor tipo n similar al ZnO y al TiO 2 que sin embargo presenta problemas de densificación en ausencia de aditivos.…”

Section: Nuevos Materiales Varistoresunclassified

Varistores cerámicos basados en óxido de cinc

Peiteado¹

2005

Bol. Soc. Esp. Ceram. Vidr.

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Los varistores basados en ZnO son dispositivos electrocerámicos caracterizados por una elevada respuesta eléctrica no lineal, que se origina en una microestructura funcional con unas características bien definidas. En el presente artículo de revisión se examina como ha tenido lugar el desarrollo de estos materiales desde su descubrimiento a principios de los años 70. No obstante, a pesar del importante avance tecnológico registrado desde entonces, numerosos aspectos básicos relacionados con su microestructura funcional siguen siendo discutidos a día de hoy.Palabras Clave: varistor, ZnO, dopantes, microestructura, procesamiento, propiedades eléctricas. Zinc oxide-based ceramic varistorsZnO-based varistors are electroceramic devices with an extremely high non-linear electrical response, originated on a functional microstructure with well defined characteristics. In the present paper the development of these materials since its discovery in the earlier seventies is reviewed. In spite of the important technological progress achieved, several essential features of its functional microstructure remain however unsolved. : varistor, ZnO, dopants, microstructure, processing, electrical properties. Keywords INTRODUCCIÓN Dispositivos protectores frente a sobretensionesEsencialmente un varistor es un resistor de impedancia variable que presenta un elevado comportamiento no lineal intensidad-voltaje. Este hecho los convierte en materiales adecuados para la protección frente a sobretensiones transitorias, entendiendo como tal un aumento no permanente del potencial eléctrico por encima del umbral de tolerancia de la tensión nominal de trabajo de un determinado sistema (1). En circuitos eléctricos las sobretensiones transitorias se presentan como resultado de una repentina liberación de energía, que bien puede haberse acumulado en el interior del propio circuito y ser liberada por una acción de conexión-desconexión del mismo, o bien puede provenir del exterior y ser inyectada o acoplada en el circuito por una acción ajena al propio diseño del circuito (1-3). Su tiempo de acción es muy corto, del orden de millonésimas de segundo. Las redes de suministro eléctrico que generan, transportan y distribuyen la energía eléctrica, las líneas telefónicas y de datos, y en general todos los equipos, máquinas y dispositivos electrónicos que operan bajo la acción de la corriente eléctrica, se encuentran expuestos a la aparición de sobretensiones transitorias que pueden provocar desde colapsos temporales prácticamente indetectables, hasta la completa destrucción de instalaciones y equipos. El problema ha recibido una mayor atención en los últimos años por el empleo masivo de componentes electrónicos y dispositivos miniaturizados en estado sólido, que son altamente sensibles a las variaciones de tensión (4-6). En la práctica y dependiendo de la aplicación, diferentes sistemas de protección se disponen entre tierra y los conductores activos, individualmente o combinados, de manera que el comportamiento limitador del circuito se acerque lo máx...

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Recent research developments in SnO2-based varistors

Cited by 77 publications

References 52 publications

Ab initio thermodynamic study of the SnO₂(110) surface in an O₂ and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO₂

Ab initio thermodynamic study of the SnO₂(110) surface in an O₂ and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO₂

From tin oxalate to (Fe, Co, Nb)-doped SnO2: Sintering behavior, microstructural and electrical features

Varistores cerámicos basados en óxido de cinc

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Recent research developments in SnO2-based varistors

Cited by 77 publications

References 52 publications

Ab initio thermodynamic study of the SnO2(110) surface in an O2 and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO2

Ab initio thermodynamic study of the SnO2(110) surface in an O2 and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO2

From tin oxalate to (Fe, Co, Nb)-doped SnO2: Sintering behavior, microstructural and electrical features

Varistores cerámicos basados en óxido de cinc

Contact Info

Product

Resources

About

Ab initio thermodynamic study of the SnO₂(110) surface in an O₂ and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO₂

Ab initio thermodynamic study of the SnO₂(110) surface in an O₂ and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO₂