Dopant Diffusion in TiSi2

1986 ◽  
Vol 77 ◽  
Author(s):  
F. M. d'Heurle ◽  
A. E. Michel ◽  
F. K. LeGoues ◽  
G. Scilla ◽  
J. T. Wetzel ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Diffusion Process ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Radioactive Tracer ◽  
Lattice Diffusion ◽  
The Other ◽  
Small Diffusion ◽  
Secondary Ion ◽  
Thick Layers

ABSTRACTDopant elements, B and Ga, P, As and Sb, and Ge as well, have been implanted into thick (350–400 nm) layers of TiSi2 prepared by Ti-Si reaction. Both B and Sb appear to be immobile, this behavior is thought to result from very small solid solubilities, rather than from very small diffusion coefficients. The other elements display about the same behavior, with detectable grain boundary diffusion at temperatures as low as 600°C, and lattice diffusion becoming considerable at 750°C, so that with the cooperation of both phenomena almost complete homogenisation of these relatively thick layers occurs in 30 minutes at 800°C. Germanium is used in lieu of a Si radioactive tracer because it can be analyzed by Secondary Ion Mass Spectroscopy. Its behavior is thought to imply that there is little equilibrium adsorption of the dopant elements at the Si/TiSi2 interface. The comparable values of the diffusion coefficients for the mobile elements confirm the anticipation that the dopants move as substitutional atoms on the Si sublattice. Results obtained with some samples implanted with both dopant and Ti indicate that in these silicon-saturated suicide layers the diffusion process is not significantly affected by small changes in stoichiometry.

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.

Mechanistic Two Stage Fission Gas Release Model

2002 ◽  
Author(s):  
Yong-Soo Kim ◽  
Chan-Bok Lee
Keyword(s):  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Diffusion Processes ◽  
Lattice Diffusion ◽  
Grain Boundary Diffusion ◽  
Factor Α ◽  
Two Stages ◽  
Grain Surface ◽  
Release Model

In this study, a mechanistic two stages model is developed which analytically simulates the two-step diffusion processes, grain lattice diffusion and grain boundary diffusion, coupled with the bubbles trap/resolution. Mathematical manipulation reveals that the release at high burn-up depend on the ratio of the diffusivities in the both processes, i.e., α ≅ Dveff/Dgbeff where Dveff and Dgbeff are effective volume and grain boundary diffusion coefficients, respectively. Thus, the ratio α is incorporated in the time-dependent third kind boundary condition at the equivalent grain surface. This model brings forth analytical solutions of the fractional release which are identical to that of either ANS5.4 or modified ANS5.4 model when α goes to the infinity. It turns out that this model describes the release behavior well in the high burn-up fuel and puts out a comparable prediction to the solution of FRAPCON-3 model under the same condition. It is also demonstrated that the new factor α not only ease the computational treatment for the high burn-up fuel performance evaluation, but also enables us to possibly separate the burn-up enhancement from the diffusion coefficients and to easily simulate the bubble-related phenomena in the grain boundary.

Grain Boundary Diffusion in Cation-Doped Superplastic 3Y-TZP

2006 ◽  
Vol 45 ◽  
pp. 1626-1631
Author(s):  
Marek Boniecki ◽  
Rafał Jakieła ◽  
Zdzislaw Librant ◽  
Wladyslaw Wesolowski ◽  
Danuta Dabrowska ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Thin Films ◽  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Tetragonal Zirconia ◽  
Grain Boundary Diffusion ◽  
Depth Profiles ◽  
Secondary Ion

The superplastic flow in tetragonal zirconia polycrystals stabilised 3mol% Y2O3 (3YTZP) is strongly affected by the dopant cations, which segregate at the grain boundary. It is proposed that this flow is controlled by grain boundary diffusion of Zr4+ ions and therefore the dopant cations should change the grain boundary diffusion. In order to prove this thesis the measurements of grain boundary diffusion coefficients were made using Hf4+ ions as tracer. Zirconia samples were doped with 1mol% of Al2O3, SiO2, MgO, MgAl2O4, GeO2 and TiO2. The tracer was deposited on the surface of the zirconia specimens by placing several drops of hafnium nitrate and then drying at 373 K. In this way, thin films of HfO 2 were obtained. The samples were heated in the range 1553 – 1773 K for 1 to 24 h. The concentration versus depth profiles were measured using secondary ion mass spectrometry (SIMS). Calculated hence grain boundary diffusion coefficients were several times bigger for doped samples than for pure 3Y-TZP samples.

Simultaneous Measurements of Lattice and Grain Boundary Diffusion Coefficients via 2-Dimensional Simulations

2010 ◽  
Vol 297-301 ◽  
pp. 978-983
Author(s):  
Ivan Blum ◽  
Alain Portavoce ◽  
Dominique Mangelinck ◽  
Jean Bernardini ◽  
Khalid Hoummada ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
The Finite Element Method ◽  
Measure Concentration ◽  
Dimensional Diffusion ◽  
Transmission Electron ◽  
Before And After ◽  
Secondary Ion

A method is presented to measure lattice and grain boundary diffusion coefficients using secondary ion mass spectroscopy and 2-dimensional diffusion simulations. SIMS is used to measure concentration profiles of implanted species before and after annealing. The as-implanted concentration profile is used as the initial condition for 2-dimensional diffusion simulations using the finite element method. The geometry of the simulation is based on the microstructure of the sample observed by transmission electron microscopy. Both lattice and grain boundary diffusion are simulated. The final 2-dimensional concentration distribution is projected on the depth axis to obtain a simulated depth profile. The diffusion coefficients are adjusted to fit the profiles measured after annealing. We find that this method allows to determine simultaneously and independently the lattice and grain boundary diffusion coefficients from the same profiles. This method is used to measure the diffusion coefficients of As in polycrystalline Ni2Si thin films. The simulations are found to fit the measured profiles with accuracy. The coefficients are measured between 550 and 700°C. An activation energy ratio Qgb/Qv is found greater than one. This result is corroborated by existing data in silicides and is compared to results in other materials for discussion.

Temperature Dependent Intermixing At The V/Ge(111) Interface

1985 ◽  
Vol 54 ◽  
Author(s):  
M. Del Giudice ◽  
R. A. Butera ◽  
J. J. Joyce ◽  
M. W. Ruckman ◽  
J. H. Weaver
Keyword(s):  
Activation Energy ◽  
High Resolution ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Boundary Diffusion ◽  
The Other ◽  
Reaction Products ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Heterogeneous Interfaces

ABSTRACTHigh resolution core level photoemission results show the temperature evolution of the V/Ge(111) interface in the range from 300 to 600 K. Three well-defined chemical environments are present for Ge at 300K (the first is the substrate and the other two are reaction products with overall shifts of−0.5 and −0.95 eV). Increasing the temperature enhances Ge outdiffusion, and a homogeneous reacted layer forms when deposition and measurements are done isothermally at 475K. The activation energy for this diffusion process is very low (5 kcal/mole), indicating the importance of grain boundary diffusion at reacting, heterogeneous interfaces.

Coercivity Enhancement of Nd-Fe-B HDDR Powder by Grain Boundary Diffusion Process with Rare-Earth Hydride

JOM ◽  
2018 ◽  
Vol 70 (5) ◽  
pp. 661-665 ◽  
Author(s):  
Hee-Ryoung Cha ◽  
Jae-Gyeong Yoo ◽  
Youn-Kyoung Baek ◽  
Dong-Hwan Kim ◽  
Hae-Woong Kwon ◽  
...  
Keyword(s):  
Rare Earth ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion

scholarly journals Dilatometry of ball milled nickel nano powder during non-isothermal sintering

2007 ◽  
Vol 39 (1) ◽  
pp. 25-29 ◽  
Author(s):  
B.B. Panigrahi ◽  
K. Das ◽  
M.M. Godkhindi
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Sintered Density ◽  
Boundary Diffusion ◽  
Lattice Diffusion ◽  
Interface Reactions ◽  
Nano Powder ◽  
Nonisothermal Heating ◽  
Sintering Mechanisms ◽  
Diffusion Mechanisms

This work attempts to evaluate the sintering mechanisms of ball milled nanocrystalline nickel during nonisothermal heating. Samples showed a sintered density of 91.2% (theoretical) and grain growth up to 414 nm at 1273K. The activation energies of 12.4, 32.0 and 51.6 kJ/mol were found for viscous flow, lattice diffusion and grain boundary diffusion mechanisms respectively. Sintering was found to be controlled by interface reactions involving surface and grain boundary diffusions.

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