FAST/SPS sintering of nanocrystalline zinc oxide—Part II: Abnormal grain growth, texture and grain anisotropy

Dargatz, Benjamin; González‐Julián, Jesús; Bram, Martin; Shinoda, Yutaka; Wakai, Fumihiro; Guillon, Olivier

doi:10.1016/j.jeurceramsoc.2015.12.008

Cited by 57 publications

(38 citation statements)

References 75 publications

(135 reference statements)

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“…ZnO/H2O presents grain sizes below 100 nm, confirming the results measured by XRD (Table I). These grain size values are in good agreement with the observed for the ZnO/H2O reported by Dargatz et al [15] at 50 MPa. In that work, the mean crystalline size was 58.8 nm at relative density of 72%, observing a texturing effect from this density due to the applied pressure.…”

Section: Resultssupporting

confidence: 92%

“…Interestingly, the grains grew preferentially in the crystallographic plane (002). The intensity of (002) peak for ZnO/Ac-H2O is rather low in comparison with the others, effect that was already observed and corresponds with the texturing due to the uniaxial pressure during the sintering process [15]. The measured crystal size was supported by SEM pictures of the fracture surfaces (Fig.…”

Section: Resultssupporting

confidence: 62%

“…As negligible grain growth up to theoretical densities of 93% was observed in a previous work of the co-authors using the same ZnO powder and amount of water [15], the data used density range considered for the calculation of the stress exponent n was kept below this theoretical density value between 80 and 85%, so that a constant grain size can be guaranteed. This is also confirmed by the present grain size measurements.…”

Section: Resultsmentioning

confidence: 99%

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Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

et al. 2018

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The sintering behavior of nanocrystalline ZnO was investigated at only 250 °C. Densification was achieved by the combined effect of uniaxial pressure and the addition of water both in a Field Assisted Sintering Technology/Spark Plasma Sintering apparatus and a warm hand press with a heater holder. The final pure ZnO materials present high densities (> 90 % theoretical density) with nano-grain sizes. By measuring the shrinkage rate as a function of applied stress it was possible to identify the stress exponent related to the densification process. A value larger than one points to non-linear relationship going beyond single solid-state diffusion or liquid phase sintering. Only a low amount of water (1.7 wt.%) was needed since the process is dictated by the adsorption on the surface of the ZnO particles. Part of the adsorbed water dissociates into H + and OH -ions, which diffuse into the ZnO crystal structure, generating grain boundaries/interfaces with high defect chemistry. As characterized by Kelvin Probe Force Microscopy, and supported by impedance spectroscopy, this highly defective grain boundary area presents much higher surface energy than the bulk. This highly defective grain boundary area with high potential reduces the activation energy of the atomic diffusion, leading to sinter the compound at low temperature.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

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Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

et al. 2018

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“…Recent work [9,11,26,27] focuses on the SPS sintering of ZnO na noparticles at low temperatures (less than 400 °C) by adding solvents (such as water, aqueous acetic acid, etc. …) to enhance densification.…”

Section: Densification Of Zno By Spark Plasma Sintering (Sps)mentioning

confidence: 99%

Influence of processing parameters on the densification and the microstructure of pure zinc oxide ceramics prepared by spark plasma sintering

Radingoana

Guillemet

Olubambi

et al. 2019

Ceramics International

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This is an author's version published in: http://oatao.univ-toulouse.fr/23777 ARTICLE INFO ABSTR ACT Keywor ds:ZnO Spark plasma slntering Nanopartlcles CeramJcs MicrostructureDue to the sensitivity of nanopowders and the challenges in controlling the grain sire and the density during the sintering of ceramics, a systernatic study was proposed to evaluate the densifi cation and the microstructure of ZnO oeramics using sparlc plasma sintering technique. Cornrnercially available ZnO powder was dried and sin tered at various parameters (ternperature (400-900 °C), pressure (250--850 MPa), atmosphere (Air/Vacuum) etc.). High pressure sintering is desirable for rnaintaining the nanostructure, though it brings a difficulty in obtaining a fully dense ceramic. Whereas, increasing the ternperature from 600 to 900 •c results in fully den sifi ed ceramics of about 99% which shows tn have big impact on the grain size. However, a high relative density of 92% is obtained at a ternperature as low as 400 •c under a pressure of 850 MPa. The application of pressure during the holding tirne seems tn lower the grain sire as compared to ceramics pressed during initial stage (room ternperature).

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“…As an important semiconducting ceramic material, ZnO is used in applications such as varistors that protect sensitive electronic devices against electrostatic discharge, 14 and it has been explored in new applications for gas sensors, 15 and in piezoelectric 16 and thermoelectric materials. 17 As a binary oxide, ZnO is also often used as a model ceramic system for fundamental studies in the sintering community, recently being demonstrated by techniques such as microwave sintering, 18,19 field-assisted-spark plasma sintering (FAST SPS), [20][21][22] and FLASH sintering. 23,24 The objective of this study is to investigate the sintering of ZnO with the CSP, noting the process variables, microstructure, and some basic properties, such as electrical conductivity, contrasted to conventional sintered materials.…”

Section: Introductionmentioning

confidence: 99%

Demonstration of the cold sintering process study for the densification and grain growth of ZnO ceramics

et al. 2016

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With the cold sintering process (CSP), it was found that adding acetic acid to an aqueous solution dramatically changed both the densities and the grain microstructures of the ZnO ceramics. Bulk densities >90% theoretical were realized below 100°C, and the average conductivity of CSP samples at around 300°C was similar to samples conventionally sintered at 1400°C. Frequently, ZnO is also used as a model ceramic system for fundamental studies for sintering. By the same procedure as the grain growth of the conventional sintering, the kinetic grain growth exponent of the CSP samples was determined as N=3, and the calculated activated energy of grain growth was 43 kJ/mol, which is much lower than that reported using conventional sintering. The evidence for grain growth under the CSP is important as it indicates that there is a genuine sintering process being activated at these low temperatures and it is beyond a pressurized densification process.

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FAST/SPS sintering of nanocrystalline zinc oxide—Part II: Abnormal grain growth, texture and grain anisotropy

Cited by 57 publications

References 75 publications

Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy

Influence of processing parameters on the densification and the microstructure of pure zinc oxide ceramics prepared by spark plasma sintering

Demonstration of the cold sintering process study for the densification and grain growth of ZnO ceramics

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