Thermal expansion of grain-boundary cracked aluminium titanate ceramics

1996 ◽  
Vol 31 (5) ◽  
pp. 1361-1365 ◽  
Author(s):  
Y. Ohya ◽  
Y. Takahashi ◽  
Z. Nakagawa
Keyword(s):  
Thermal Expansion ◽  
Grain Boundary ◽  
Aluminium Titanate ◽  
Titanate Ceramics

Effect of grain boundary cracks on the corrosion behaviour of aluminium titanate ceramics in a molten aluminium alloy

2012 ◽  
Vol 54 ◽  
pp. 90-96 ◽  
Author(s):  
Makoto Tanaka ◽  
Kazumi Kashiwagi ◽  
Naoki Kawashima ◽  
Satoshi Kitaoka ◽  
Osamu Sakurada ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Aluminium Alloy ◽  
Corrosion Behaviour ◽  
Molten Aluminium ◽  
Aluminium Titanate ◽  
Titanate Ceramics

Degradation of Rocks, Through Cracking Caused by Differential Thermal Expansion, in Relation to Nuclear Waste Repositories

1981 ◽  
Vol 6 ◽  
Author(s):  
J.R. Mclaren ◽  
R.W. Davidge ◽  
I. Titchell ◽  
K. Sincock ◽  
A. Bromley
Keyword(s):  
Thermal Expansion ◽  
Grain Boundary ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Crack Density ◽  
Granitic Rocks ◽  
Multiphase Materials ◽  
Thermal Expansion Behaviour ◽  
Waste Repositories ◽  
Expansion Behaviour

ABSTRACTHeating to temperatures up to 500°C, gives a reduction in Young's modulus and increase in permeability of granitic rocks and it is likely that a major reason is grain boundary cracking. The cracking of grain boundary facets in polycrystalline multiphase materials showing anisotropic thermal expansion behaviour is controlled by several microstructural factors in addition to the intrinsic thermal and elastic properties. Of specific interest are the relative orientations of the two grains meeting at the facet, and the size of the facet; these factors thus introduce two statistical aspects to the problem and these are introduced to give quantitative data on crack density versus temperature. The theory is compared with experimental measurements of Young's modulus and permeability for various rocks as a function of temperature. There is good qualitative agreement, and the additional (mainly microstructural) data required for a quantitative comparison are defined.

Effects of La Doping on the Structural and Dielectric Properties of Barium Titanate Ceramics

2014 ◽  
Vol 975 ◽  
pp. 36-41
Author(s):  
Marcelo S. Silva ◽  
Nilson S. Ferreira
Keyword(s):  
Grain Boundary ◽  
Solid State Reaction Method ◽  
Boundary Region ◽  
Homogeneous Distribution ◽  
Sem Images ◽  
Tetragonal Crystal ◽  
Brick Layer Model ◽  
Lower Temperature ◽  
Clear Shift ◽  
Titanate Ceramics

Polycrystalline samples of Ba1-xLaxTiO3 (x = 0.0, 0.002, 0.004) were prepared by a standard high-temperature solid-state reaction method. XRD studies confirmed the formation of a polycrystalline compound with a tetragonal crystal structure. SEM images suggested the presence of a polycrystalline microstructure with certain degree of porosity, and the grains appeared to be distributed inhomogeneously throughout the pallet samples. Dielectric studies indicated a ferroelectric–paraelectric phase transition with a clear shift in the Curie temperature (Tc) of BaTiO3 towards a lower temperature upon doping. The brick-layer model was used to study the potential barrier and the structure of the grain-boundary region of the Ba9.998La0.002TiO3 and Ba9.996La0.004TiO3 ceramics. These ceramics exhibited good density and a homogeneous distribution of the grains. The thickness of the grain-boundary region was calculated to be approximately 200 nm.

Diffusion and solubility of holmium ions in barium titanate ceramics

2004 ◽  
Vol 19 (12) ◽  
pp. 3512-3520 ◽  
Author(s):  
Junichi Itoh ◽  
Hajime Haneda ◽  
Shunichi Hishita ◽  
Isao Sakaguchi ◽  
Naoki Ohashi ◽  
...  
Keyword(s):  
Barium Titanate ◽  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Diffusion Mechanism ◽  
Annealed Sample ◽  
Lattice Diffusion ◽  
Grain Boundary Diffusion ◽  
A Site ◽  
Titanate Ceramics

Ho ion solubility and diffusivity were evaluated in barium titanate ceramics in which Ho ions were implanted with an accelerating voltage of 500 keV. The depth profile of the ions was composed of three regions in the post-annealed sample: the first was the precipitation region, the second was a region created by lattice diffusion of Ho ions, and the third was a region created by grain-boundary diffusion. The Ho lattice diffusion characteristics were similar to those of Ni ion diffusion in barium titanate ceramics, and we concluded that the diffusion mechanism was the same as that responsible for Ni ions. The Ho ions diffused through the B-site (Ti-site) and were then exchanged with A-site ions. This mechanism suggests that a small number of Ho ions dissolved in the B-site. Preferential grain-boundary diffusion was also observed. The grain-boundary diffusion coefficients were four to five orders of magnitude larger than the volume diffusion coefficients. The solubility of Ho ions was estimated to be a few thousand parts per million in barium titanate ceramics.

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