Grain-Growth Phenomena in ZnO-Based Ceramics

2007 ◽  
Vol 558-559 ◽  
pp. 857-862 ◽  
Author(s):  
Slavko Bernik ◽  
Mateja Podlogar ◽  
Nina Daneu ◽  
Aleksander Rečnik
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Growth Mechanism ◽  
Pyrochlore Phase ◽  
Early Stages ◽  
Zno Ceramics

Grain growth in ZnO ceramics doped with 0.01 and 0.02 mol.% Bi2O3 and Sb2O3 in amounts appropriate for Sb2O3/Bi2O3 ratios of 0.8, 1.0 and 1.2, sintered at 1200oC for 2 and 10 hours, was investigated. Grain growth is promoted by a sufficient amount of the Bi2O3 liquid phase at the grain boundaries and also by the presence of IBs in the ZnO grains. While the doping of ZnO with such small amounts of Bi2O3 caused the exaggerated growth of some grains, the addition of Sb2O3 resulted, via the IBs-induced grain-growth mechanism, in uniform grain growth and the presence of IBs in most of the ZnO grains. The formation of the pyrochlore phase bounds the Bi2O3 and Sb2O3, which affects, depending on the Sb2O3/Bi2O3 ratio, the occurrence of the Bi2O3 liquid phase and also the amount of available Sb2O3 for the nucleation of IBs in the ZnO grains during the early stages of sintering. As a result, it influences the grain growth.

scholarly journals Grain Growth Behavior of 0.95(Na0.5Bi0.5)TiO3–0.05BaTiO3 Controlled by Grain Shape and Second Phase

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1344 ◽  
Author(s):  
Sang-Chae Jeon ◽  
John G. Fisher ◽  
Suk-Joong L. Kang ◽  
Kyoung-Seok Moon
Keyword(s):  
Liquid Phase ◽  
Grain Growth ◽  
Growth Mechanism ◽  
Driving Force ◽  
Grain Shape ◽  
Growth Behavior ◽  
Second Phase ◽  
Two Dimensional ◽  
Grain Growth Behavior ◽  
Powder Compacts

The grain growth behavior of 0.95(Na0.5Bi0.5)TiO3 –0.05BaTiO3 (mole fraction, NBT–5BT) grains was investigated with excess Bi2O3 addition. The powder compacts of NBT–5BT were sintered at 1200 °C for various sintering times and with various amounts of Bi2O3 (0.1, 1.5, 4.0 and 10.0 mol%). When Bi2O3 was added to round-edged cubic NBT–5BT, the grain shape changed to a more faceted cube and the amount of liquid phase increased during sintering. A more faceted cubic grain shape indicates an increase in the critical driving force for appreciable growth of grains. However, obvious abnormal grain growth did not appear in any of the NBT–5BT samples with excess Bi2O3. The amount of liquid phase increased as the amount of Bi2O3 increased. Therefore, the rate of grain growth could be decreased by the increasing the distance for the diffusion of atoms. These observations allowed us to conclude that the growth of Bi2O3-excess NBT–5BT grains is governed by the growth of facet planes via the two-dimensional nucleation grain growth mechanism during changing grain shape and amount of liquid.

Grain growth and the microstructural effects on the properties of YBa2Cu3O7−y superconductor

1990 ◽  
Vol 5 (9) ◽  
pp. 1819-1826 ◽  
Author(s):  
C. T. Chu ◽  
B. Dunn
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Tetragonal Phase ◽  
Sintering Temperature ◽  
Oxygen Stoichiometry ◽  
Microstructural Development ◽  
Prolonged Annealing ◽  
Microstructural Effects ◽  
Oxygenation Rate

The microstructural development and grain growth of YBa2Cu3O7−y ceramics at 925, 950, and 975 °C were studied. Densification occurred quite rapidly at temperatures below 925 °C. The grain growth of YBa2Cu3O7−y followed a D5 − D50 = Kt relation when sintered at 925 and 950 °C. At 975 °C, the kinetics changed to cubic (D3) behavior, which can be attributed to the formation of a liquid phase at grain boundaries. A trend of decreasing Jc with increasing sintering temperature was observed. Other properties including Tc and the width of the transition were virtually unaffected by the change in microstructure. Without prolonged annealing, a relatively homogeneous oxygen stoichiometry of 6.8 was obtained for fairly dense samples (>93% of theoretical). These results suggest that the oxygenation rate of YBa2Cu3O7−y was quite rapid between the tetragonal phase and the orthorhombic composition of YBa2Cu3O6.8.

Mechanism of grain growth in liquid-phase-sintered β–SiC

1999 ◽  
Vol 14 (11) ◽  
pp. 4291-4293 ◽  
Author(s):  
Young-Wook Kim ◽  
Mamoru Mitomo ◽  
Guo-Dong Zhan
Keyword(s):  
Liquid Phase ◽  
Grain Growth ◽  
Growth Mechanism ◽  
Weight Fraction ◽  
Annealed Specimen ◽  
Controlled Growth ◽  
Diffusion Controlled ◽  
Oxynitride Glass

The mechanism for grain growth of β–SiC was investigated by annealing hot-pressed β–SiC–oxynitride glass (Y–Mg–Si–Al–O–N) ceramics at 1800 °C. An observed decrease in grain growth with increasing weight fraction of liquid confirms a diffusion-controlled growth mechanism in the system. The growth of nearly spherical β–SiC grains in the annealed specimen also supports the above conclusion.

Enhanced Plasticity of Pure Nickel Processed by HPT Consolidation of Rapid Quenched Ribbons

2016 ◽  
Vol 838-839 ◽  
pp. 122-126
Author(s):  
Alexander P. Zhilyaev
Keyword(s):  
Liquid Phase ◽  
Low Temperature ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Nanocrystalline Materials ◽  
Pure Nickel ◽  
Superplastic Behavior ◽  
Half Century ◽  
Pure Metals ◽  
Future Work

Although superplasticity has intensively been studied for half century, few observations have been reported for pure metals due to fast grain growth at temperatures required for superplasticity. With developing of nanocrystalline materials, there was a hope that superplasticity could be obtained in a number of pure metals. Indeed, low temperature superplasticity in pure nickel was reported in pioneering work in 1999, later superplastic feature of nanonickel was attributed to sulfur presence in grain boundaries. Recently, it was concluded that superplasticity it is not related to the presence of sulfur at grain boundaries or a liquid phase at grain boundaries. Thereby, the phenomenon of superplasticity in pure metals is still far away for our understanding and it requires future work. This report is devoted to reassessment of superplastic behavior of nanonickel and it provides new results on enhanced plasticity of pure nickel processed by HPT consolidation of rapid quenched ribbons.

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

scholarly journals Liquid‐Assisted Grain Growth: Effect of Cu–Sn–Se Liquid Phase on Grain Growth and Efficiency of CZTSSe Solar Cells (Adv. Energy Mater. 14/2020)

2020 ◽  
Vol 10 (14) ◽  
pp. 2070060
Author(s):  
Se‐Yun Kim ◽  
Dae‐Ho Son ◽  
Seung‐Hyun Kim ◽  
Young‐Ill Kim ◽  
Sammi Kim ◽  
...  
Keyword(s):  
Solar Cells ◽  
Liquid Phase ◽  
Grain Growth ◽  
Growth Effect ◽  
Energy Mater

Microstructure of Polycrystalline MgO Penetrated by a Silicate Liquid

1996 ◽  
Vol 2 (3) ◽  
pp. 113-128 ◽  
Author(s):  
Sundar Ramamurthy ◽  
Michael P. Mallamaci ◽  
Catherine M. Zimmerman ◽  
C. Barry Carter ◽  
Peter R. Duncombe ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Glassy Phase ◽  
Silicate Liquid ◽  
Two Phase ◽  
The Matrix ◽  
Devitrification Process ◽  
Phase Mixture

Dense, polycrystalline MgO was infiltrated with monticellite (CaMgSiO4) liquid to study the penetration of liquid along the grain boundaries of MgO. Grain growth was found to be restricted with increasing amounts of liquid. The inter-granular regions were generally found to be comprised of a two-phase mixture: crystalline monticellite and a glassy phase rich in the impurities present in the starting MgO material. MgO grains act as seeding agents for the crystallization of monticellite. The location and composition of the glassy phase with respect to the MgO grains emphasizes the role of intergranular liquid during the devitrification process in “snowplowing” impurities present in the matrix.

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