Preparation and Electric Properties of Dense Nanocrystalline Zinc Oxide Ceramics

Gao, Lian; Li, Qiang; Luan, Weiling; Kawaoka, Hirokazu; Sekino, Tohru; Niihara, Koichi

doi:10.1111/j.1151-2916.2002.tb00214.x

Cited by 96 publications

(59 citation statements)

References 13 publications

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“…[135][136][137][138] For example Macary et al, 137 employed the SPS technique to sinter ZnOBi 2 O 3 nanomaterial (10 nm) at temperatures ranging from 550 to 600…”

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confidence: 99%

Advances in the synthesis of ZnO nanomaterials for varistor devices

et al. 2013

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adZnO based varistors are widely used for overvoltage protection in many electrical and electronic circuits, at voltages ranging from a few to over a million volts. By careful control of the microstructure, through nanostructuring by chemical routes, it should be possible to produce varistors with high breakdown voltage (V c ), as this is proportional to the number of active grain boundaries in the sintered body. This property is particularly important for the production of the small-sized varistors needed for modern electronic instruments such as tablet computers and mobile phones. The current review will outline the recent advances in the chemical processing (e.g. sol-gel, combustion synthesis plasma pyrolysis, micro-emulsion synthesis and precipitation routes) of varistors from ZnO nanomaterials and the properties of these materials. Uncontrolled grain growth at higher temperature is highlighted as a major challenge for obtaining desirable electrical properties for nano-varistors. Various novel sintering techniques such as step-sintering, spark plasma and microwave sintering methods are expected to deliver a varistor with controlled grain growth and optimum electrical characteristics.

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“…[135][136][137][138] For example Macary et al, 137 employed the SPS technique to sinter ZnOBi 2 O 3 nanomaterial (10 nm) at temperatures ranging from 550 to 600…”

mentioning

confidence: 99%

Advances in the synthesis of ZnO nanomaterials for varistor devices

et al. 2013

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“…Instead of using an external heat source, pulsed current passes through the electrically conducting pressure dyes, thereby generating the sintering temperature [21][22][23]. SPS has been used to generate dense ceramics with minimum grain growth [19] for many applications [23], including electroceramics [24,25], composites [26,27], bioceramics [28], thermoelectric materials [29], and transparent polycrystalline alumina (PCA) [30]. Only a few publications present SPS sintering of ZnO nanopowders, even though there is great potential in this technique.…”

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confidence: 99%

Synthesis and Sintering of ZnO Nanopowders

et al. 2017

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Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders' nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv 50~6 0 nm, easily redispersable) by using a continuous Segmented Flow Tubular Reactor (SFTR), which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a "scale-out" concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 • C and 1100 • C, and Spark Plasma Sintering (SPS) at 900 • C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 • C, while also limiting the grain growth, thus leading to a nanostructured material.

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“…The spark plasma sintering (SPS) process is generally used in the densification of nanocrystalline TiO 2 samples [12][13][14]. The SPS process enhances densification of the sample by application of pulsed voltage and uniaxial pressure to the specimen during sintering.…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of Fe-doped TiO₂nanoparticles synthesised by sol–gel route

Singh

Yadav

Singh

et al. 2013

Journal of Experimental Nanoscience

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Fe-doped nanocrystalline samples of titanium oxide have been synthesised by sol-gel route and conventional sintering process at 450 C under atmospheric conditions. These samples are characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and dielectric property measurement. Samples with Fe content more than 4 mole% crystallises in rutile phase and those with less than 4 mole% crystallises in anatase phase. Nanocrystallite size has been controlled by Fe doping. Crystallite size was found to decrease with Fe concentration in the anatase phase samples whereas reverse happens in rutile phase samples of titanium oxide. There is a slight variation in numerical values of crystallite sizes measured by the two techniques: TEM and XRD peak broadening. The highest crystallite size was 86 nm in 10 mole% Fe-doped samples and the lowest 20 nm in 4 mole% Fe-doped sample. Large dispersions and anomalous values of the dielectric constant, "r were observed at low frequency in anatase phase samples. Rutile phase samples exhibit little dispersion over the measurement frequency range of 20 Hz to 10 MHz. The dielectric constant value of all the samples stabilises to a constant value at higher frequencies. This value is dependent on the final crystalline phase but independent of the crystallite size. The anomalous dielectric behaviour of anatase samples at low frequencies is assigned to the adsorbed -OH ions on the sample surface.

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Preparation and Electric Properties of Dense Nanocrystalline Zinc Oxide Ceramics

Cited by 96 publications

References 13 publications

Advances in the synthesis of ZnO nanomaterials for varistor devices

Advances in the synthesis of ZnO nanomaterials for varistor devices

Synthesis and Sintering of ZnO Nanopowders

Dielectric properties of Fe-doped TiO₂nanoparticles synthesised by sol–gel route

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Preparation and Electric Properties of Dense Nanocrystalline Zinc Oxide Ceramics

Cited by 96 publications

References 13 publications

Advances in the synthesis of ZnO nanomaterials for varistor devices

Advances in the synthesis of ZnO nanomaterials for varistor devices

Synthesis and Sintering of ZnO Nanopowders

Dielectric properties of Fe-doped TiO2nanoparticles synthesised by sol–gel route

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Dielectric properties of Fe-doped TiO₂nanoparticles synthesised by sol–gel route