Preparation and characterization of nanocrystalline ZnO based materials for varistor applications

Viswanath, R. N.; Ramasamy, S.; Ramamoorthy, R.; Jayavel, P.; Nagarajan, T.

doi:10.1016/0965-9773(95)00229-4

Cited by 94 publications

(51 citation statements)

References 5 publications

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“…3, 5,6,8 The temperature required for sintering also depends on the particle size and on the distribution of dopants among the individual grains. Nanometre-sized material contains large grain boundary volumes and should therefore yield more varistor active grain boundaries per unit volume, allowing one to develop a better device with smaller dimensions.…”

Section: 5mentioning

confidence: 99%

“…3, 5,8 Thus, careful control of the microstructure is required to produce the perfect varistor. Nanoparticles yield a narrow grain size distribution and can be sintered at a lower temperature compared to coarse grained ceramics.…”

Section: 5mentioning

confidence: 99%

“…3, 5,6,[8][9][10][11][12][13][14][15][16][17][18][19] We have recently found that nano-ZnO synthesised from zinc acetate dihydrate and oxalic acid dihydrate either by a solution route 18 or by a solid-state pyrolysis route 19 can be used to produce varistors with an improved breakdown voltage. Furthermore, core-shelltype varistor materials fabricated by coating metal salts on previously calcined ZnO nanoparticles were found to give superior electrical properties, which were attributed to better homogeneity of additive ions among the ZnO grains.…”

Section: 5mentioning

confidence: 99%

“…[8][9][10][11][12][13][14][15][16][17][18][19] In particular inhomogeneous microstructures can cause degradation of varistors during electrical operation.…”

Section: 5mentioning

confidence: 99%

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High performance ZnO varistors prepared from nanocrystalline precursors for miniaturised electronic devices

Pillai

Kelly

McCormack³

et al. 2008

J. Mater. Chem.

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An industrially viable solution-based processing route using minimal amounts of solvent has been used to prepare bulk quantity nanopowders (average particle size 15 AE 3 nm) for the fabrication of ZnO varistors. The xerogels, calcined powders and sintered materials were fully characterised. The preparation of varistors from nanopowders has been optimised by studying the effect of temperature on grain growth, densification and breakdown voltage. The varistors are prepared by sintering at 1050 C for 2 hours, a temperature that is significantly lower than that used in the current industrial process. Highly dense varistor discs prepared from the sintered material produce devices, with a breakdown voltage 85% higher than that of commercial varistors, making them suitable for use in miniaturised electronic circuitry. Improved performance of these materials has been attributed to the small grain size and better dispersion of additives on ZnO grains.

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Section: 5mentioning

confidence: 99%

Section: 5mentioning

confidence: 99%

Section: 5mentioning

confidence: 99%

“…[8][9][10][11][12][13][14][15][16][17][18][19] In particular inhomogeneous microstructures can cause degradation of varistors during electrical operation.…”

Section: 5mentioning

confidence: 99%

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High performance ZnO varistors prepared from nanocrystalline precursors for miniaturised electronic devices

Pillai

Kelly

McCormack³

et al. 2008

J. Mater. Chem.

View full text Add to dashboard Cite

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“…[1][2][3][4] The method of preparation, crystalline size and additive homogeneity are the critical parameters to produce a better varistor material. [5][6][7][8][9][10][11][12] Varistors with inhomogeneous microstructure can cause a large spread in current/voltage characteristics due to high local currents and this leads to the degradation of the varistor during electrical operation. 2,6,8,11 It is well documented that electrical and electronic characteristics can be altered by varying the microstructure at the grain boundaries, 2,[11][12][13][14][15] and careful control of the microstructure is required to produce a high performance varistor.…”

Section: Introductionmentioning

confidence: 99%

The effect of processing conditions on varistors prepared from nanocrystalline ZnO

Pillai

Kelly

McCormack³

et al. 2003

J. Mater. Chem.

143

153

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Nanoparticles of ZnO were prepared by the reaction of ethanolic solutions of zinc acetate and oxalic acid followed by drying (80 uC) and calcination (500 uC). Subsequently varistor materials were fabricated from this nanoparticular ZnO via two separate routes:-a) from a ''core shell'' material using metal salts as additives; b) by using a conventional solid state mixing of metal oxides. Sintering (1050 uC) and subsequent electrical studies were carried out for each of these samples and they were compared with commercial varistor samples prepared under similar conditions. ''Core shell'' type varistor material showed considerably higher breakdown voltage (V c~8 50 ¡ 30 V mm 21 ) as compared to a sample prepared by mixing with metal oxides (V c~6 83 ¡ 30 V mm 21 ) or commercial varistor discs (V c~5 07 ¡ 30 V mm 21 ). The high breakdown voltage obtained is attributed to the formation of more varistor-active grain boundaries per unit area.

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Transition Metal Oxides

Landau

2002

Handbook of Porous Solids

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Preparation and characterization of nanocrystalline ZnO based materials for varistor applications

Cited by 94 publications

References 5 publications

High performance ZnO varistors prepared from nanocrystalline precursors for miniaturised electronic devices

High performance ZnO varistors prepared from nanocrystalline precursors for miniaturised electronic devices

The effect of processing conditions on varistors prepared from nanocrystalline ZnO

Transition Metal Oxides

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