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

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.

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Grain Growth Behavior of Al2O3-ZrO2 with a Small Amount of Zirconia

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.535 ◽

2007 ◽

Vol 561-565 ◽

pp. 535-538 ◽

Cited By ~ 3

Author(s):

M. Nagashima ◽

Motozo Hayakawa

Keyword(s):

Growth Inhibition ◽

Grain Boundaries ◽

Grain Growth ◽

Sintering Temperature ◽

Growth Behavior ◽

Pinning Effect ◽

Grain Growth Behavior ◽

Good Agreement ◽

Zirconia Content

Grain growth behavior in Al2O3 with a small amount of ZrO2 (< 5 vol%) was examined. Grain growth of Al2O3 was retarded by zirconia particles, despite the small amount of added zirconia. The fraction of the zirconia particles embedded within alumina grains (intragranular zirconia particles) increased with decreasing zirconia content and increasing sintering temperature. Grain growth inhibition of alumina in the Al2O3-ZrO2 showed good agreement with the prediction of modified Zener’s pinning effect by the zirconia particles on grain boundaries.

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Low-temperature sintering of PNW–PMN–PZT piezoelectric ceramics

Journal of Materials Research ◽

10.1557/jmr.2007.0322 ◽

2007 ◽

Vol 22 (9) ◽

pp. 2410-2415 ◽

Cited By ~ 7

Author(s):

Pengxian Lu ◽

Mankang Zhu ◽

Dehe Xu ◽

Wenjun Zou ◽

Zhengxin Li ◽

...

Keyword(s):

Low Temperature ◽

Phase Boundary ◽

Grain Boundaries ◽

Relative Density ◽

Grain Growth ◽

Piezoelectric Properties ◽

Sintering Temperature ◽

Secondary Phase ◽

Low Temperature Sintering ◽

Densification Process

For low-temperature firing of Pb0.94Sr0.06(Ni1/2W1/2)0.02(Mn1/3Nb2/3)0.07(Zr0.51Ti0.49)0.91O3 (PNW–PMN–PZT) system, BiFeO3 is selected as the sintering agent. In this study, the effects of BiFeO3 addition and sintering temperature on the microstructures and piezoelectric properties of the ceramics were investigated in detail. The ceramic with 10 mol% BiFeO3 sintered at 950 °C possesses optimal microstructure and piezoelectric properties. However, with the increase of sintering temperature the lower relative density, abnormal grain growth, and secondary phase accumulated at grain boundaries are observed, which deteriorates the piezoelectric properties. For the ceramics with different BiFeO3 addition sintered at 950 °C, the densification process and the grain growth are improved by suitable BiFeO3, while the morphotropic phase boundary (MPB) moving to the Ti-rich direction and the shrinkage of crystal cell occur. However, extra BiFeO3 inhabits the grain growth and introduces more cavities into the materials. Because of the microstructural changes that accompany the addition of BiFeO3 and the resulting decrease in sintering temperature, the maximum values of the piezoelectric properties are attained. By doping with 10 mol% BiFeO3, the sintering temperature of the PNW–PMN–PZT system can be lowered successfully from 1200 to 950 °C, while the excellent electric properties are kept.

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Grain Growth and Electric Properties of Lead-Free BaTiO3 Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.368-372.1919 ◽

2008 ◽

Vol 368-372 ◽

pp. 1919-1922

Author(s):

Chun Huy Wang

Keyword(s):

Liquid Phase ◽

Grain Growth ◽

Inverse Relationship ◽

Piezoelectric Properties ◽

Sintering Temperature ◽

Glass Frit ◽

Lead Free ◽

Batio3 Ceramic ◽

Capillary Action ◽

Dielectric And Piezoelectric Properties

Many lead-free materials, such as Bi-based compounds, BaTiO3 or alkaline niobate compound, have been intensively studied. The microstructure and characteristics of BaTiO3 ceramics are significantly influenced by addition of 4PbO-B2O3. Under low sintering temperatures, the grain growth of BaTiO3 ceramic is enhanced by capillary action, rearrangement and solution-reprecipitation of the liquid phase. At high sintering temperatures, exaggerated grain growth of BaTiO3 ceramic is restrained by the presence of a liquid phase. The theory of grain growth in the presence of a liquid phase is examined in terms of the equation Rn = k× t. The grain growth kinetic exponent, n, has an inverse relationship with the rate of grain growth. With suitable amounts of glass frit and an optimized sintering temperature, the density is enhanced and the values of the dielectric and piezoelectric properties are improved.

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Grain Growth Anomaly in Ti-rich Strontium Titanate as Revealed by Electron Microscopy

Microscopy and Microanalysis ◽

10.1017/s143192761201327x ◽

2012 ◽

Vol 18 (S5) ◽

pp. 123-124

Author(s):

L. Amaral ◽

M. Fernandes ◽

A. M. R. Senos ◽

P. M. Vilarinho ◽

M. P. Harmer

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Grain Boundaries ◽

Grain Growth ◽

Strontium Titanate ◽

Structural Changes ◽

Sintering Temperature ◽

Size Distributions ◽

High Tunability ◽

Grain Size Distributions

An anomaly in the dependence of the kinetics of grain growth on the temperature for strontium titanate (ST) ceramics is reported in this work. It consists of a decrease of the grain size with increasing sintering temperature. Recently, a drop in the grain boundary mobility of ST in the same temperature range was reported. These observations imply an unusual decrease of the grain size with the increase of the sintering temperature, in agreement with our present results. Although the mobility drop was related to structural changes in grain boundaries, the exact mechanism involved is still unknown. The understanding of this anomaly may offer an alternative way of controlling the microstructure and tuning the dielectric response of ST based compositions without the use of dopants. ST is characterized by high dielectric permittivity, high tunability and low dielectric losses, and is thus a particularly interesting material for capacitor or tunable microwave devices. These properties are very dependent on the stoichiometry, structure and microstructure, in which the role of grain boundaries is fundamentally important. Indeed, increasing attention has been paid to grain boundary structures and nonstoichiometry and to its relation with microstructure and electrical properties. Densification proceeds faster with decreasing Sr/Ti ratio (Ti-rich compositions). Sr-rich samples show narrow grain size distributions, while Ti excess favors enlarged grain size distributions and faceting of the grain boundaries.

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Grain-Growth Phenomena in ZnO-Based Ceramics

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.857 ◽

2007 ◽

Vol 558-559 ◽

pp. 857-862 ◽

Cited By ~ 2

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.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.838-839.122 ◽

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.

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Elucidation of block boundaries as the dissolution channels in hydrated cement

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109562 ◽

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.

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Gravitational effects on microstructural development in liquid phase sintered alloys

Metal Powder Report ◽

10.1016/s0026-0657(97)84687-5 ◽

1997 ◽

Vol 53 (7-8) ◽

pp. 39

Author(s):

T Courtney

Keyword(s):

Liquid Phase ◽

Microstructural Development ◽

Gravitational Effects ◽

Sintered Alloys

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Synthesis and Na+ Ion Conductivity of Stoichiometric Na3Zr2Si2PO12 by Liquid-Phase Sintering with NaPO3 Glass

Materials ◽

10.3390/ma14143790 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3790

Author(s):

Yongzheng Ji ◽

Tsuyoshi Honma ◽

Takayuki Komatsu

Keyword(s):

Solid State ◽

Liquid Phase ◽

Sintering Temperature ◽

Liquid Phase Sintering ◽

Ion Conductivity ◽

X Ray Diffraction ◽

Conventional Solid State Reaction ◽

X Ray ◽

Sintering Time ◽

Lower Activation

Sodium super ionic conductor (NASICON)-type Na3Zr2Si2PO12 (NZSP) with the advantages of the high ionic conductivity, stability and safety is one of the most famous solid-state electrolytes. NZSP, however, requires the high sintering temperature about 1200 °C and long sintering time in the conventional solid-state reaction (SSR) method. In this study, the liquid-phase sintering (LPS) method was applied to synthesize NZSP with the use of NaPO3 glass with a low glass transition temperature of 292 °C. The formation of NZSP was confirmed by X-ray diffraction analyses in the samples obtained by the LPS method for the mixture of Na2ZrSi2O7, ZrO2, and NaPO3 glass. The sample sintered at 1000 °C for 10 h exhibited a higher Na+ ion conductivity of 1.81 mS/cm at 100 °C and a lower activation energy of 0.18 eV compared with the samples prepared by the SSR method. It is proposed that a new LPE method is effective for the synthesis of NZSP and the NaPO3 glass has a great contribution to the Na+ diffusion at the grain boundaries.

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