Grain Boundary Diffusion Parameter Research Articles

Yttrium diffusion in α-alumina single crystal

Yttrium bulk diffusion in single crystals of α-alumina is investigated by the SIMS technique, in the temperature range 1150–1500 °C. The bulk diffusion coefficients obey the relation: D( Y)(1150–1500 °C) = 1.2 10 −10 exp (−295(kJ mol −1)/RT) (m 2 s −1). These values are close to those of chromium diffusion in alumina, although the size of Y 3+ ion is significantly higher than that of Cr 3+ ion. The results are used to calculate the parameters of yttrium grain boundary diffusion in alumina, from the penetration profiles obtained in a previous work in polycrystals by the radiotracer technique.

Temperature and orientation dependences of the grain-boundary diffusion coefficient of antimony in copper bicrystals

An investigation is made of the diffusion of antimony through the bulk and along grain boundaries in copper bicrystals containing a symmetric 〈100〉 misorientation boundary with misorientation angles from 20 to 37.2°. The bicrystals are grown by the method of horizontal zone recrystallization. The temperature range for these studies is 480–580 °C, where the solubility of Sb in Cu is about 6 atomic % and practically temperature-independent. The concentration profiles are obtained by x-ray spectral microanalysis, and the grain-boundary diffusion parameters are computed by the method of Whipple and Suzuoka. The orientation dependence of the triple product P=sδD b (where s is the segregation coefficient, δ the width of the grain boundary, and D b the grain-boundary diffusion coefficient) is nonmonotonic, with a maximum for the special ∑5 misorientation boundary (36.9°). The effective activation energy for grain-boundary diffusion ranges from ∼70 kJ/mol for ∑5 to140 kJ/mol for general boundaries.

Segregation effect on grain-boundary diffusion in thin metallic films

The diffusion in AuCu and PtCu thin films has been studied by Rutherford backscattering sperctrometry (RBS) under the kinetic regimes B (within the temperature interval of 175–290 °C) and C (room temperature). The 1.5–2.0 MeV He + RBS spectra were taken using 14–18 keV resolution. The RBS spectra were changed to depth-concentration profiles for both bulk and grain boundary (GB) diffusion. Under kinetic regime C the absolute values of GB diffusion coefficients were obtained. Under kinetic regime B the triple products δKD b (δ is the GB width, D b is the GB diffusion coefficient, K is the enrichment ratio) were obtained using the Whipple and Gilmer-Farrell models. The activation energies for GB diffusion of Au into Cu films and Cu into Au films are close to 0.95–0.98 eV atom −1, whereas the activation energy for GB diffusion of Pt into Cu films is equal to 1.25 eV atom −1. The comparison between the data on the GB diffusion for kinetic regime B extrapolated to room temperature and the data on the GB diffusion for kinetic regime C enables one to derive the product δK and to separate the contribution of segregation to the parameters of GB diffusion for the systems under study.

Segregation Effect and its Influence on Grain Boundary Diffusion in Thin Metallic Films

ABSTRACTThe diffusion in Au-Cu and Pt-Cu thin films has been studied by Rutherford backscattering spectrometry (RBS) under the kinetic regime “B” (within the temperature interval of 175–290°C) and “C” (room temperature). The 1,5-2,0 MeV He+ RBS spectra were taken using 14–18 keV resolution. The RBS spectra were changed to depth-concentration profiles for both bulk and grain boundary (GB) diffusion. Under the kinetic regime “C” the absolute values of GB diffusion coefficients were obtained. Under the kinetic regime “B” the triple products δKDb, (δ is the GB width, Db is the GB diffusion coefficient, K is the enrichment ratio) were obtained using Whipple’s and Gilmer-Farrell’s models. The activation energies for both GB diffusion and bulk diffusion were determined for Au-Cu system as well as for Pt-Cu system. The comparison between the data on the GB diffusion for kinetics “B” extrapolated to room temperature and the data on the GB diffusion for the kinetics “C” enables one to derive the product δK and to separate the contribution of segregation into the parameters of GB diffusion for systems under study.

Zirconium–Hafnium Interdiffusion in Polycrystalline Fluorite‐Cubic CeO2─ZrO2─HfO2 Solid Solution

Zr–Hf interdiffusion was studied in the temperature range of 1650° to 1850°C in air for polycrystalline fluorite‐cubic systems of 90CeO2·10(Zr1‐xHfx)O2 and 60CeO2·40(Zr1‐xHfx)O2. Lattice and grain‐boundary diffusion parameters were calculated from the Zr–Hf concentration distributions by using the grain‐boundary diffusion equation of Oishi and Ichimura. The cation iattice diffusivity was close to that in the fluorite‐cubic Y2O2‐ZrO2 solid solution.

Possible approach to quantitative description of the compaction process with hot isostatic pressing of polydispersed materials

A known approach to mathematical description of the compaction process for monodispersed spherical powders under hot isostatic compression is developed for actual polydispersed powders. Calculated compaction curves for silicon nitride agree satisfactorily with experimental data. Estimation of grain-boundary diffusion parameters gives values of 6 · 10−18 m3/sec and 180 kJ/mole which corre-spond to results obtained in other experimental works.

A model for diffusion along a moving grain boundary

A model of grain boundary (GB) diffusion along an isolated moving GB is proposed based on the Fisher model. The GB is assumed to move with a constant velocity v. Analytical solutions of the model are obtained, and methods of GB diffusion parameters determination in different experimental conditions are discussed. Application of conventional methods, like the 6 5 - method , to moving GBs results in essentially (by a factor of about 1 2 vt( Dt) − 1 2 underestimated values of the product D′ δ. For more correct estimation of D′ δ, the proposed exponential solution should be used in such cases. A detailed classification of kinetic regimes in a bicrystal, containing stationary and moving GBs, is introduced. A kinetic diagram, useful in designing GB diffusion experiments, is proposed.

Cation Interdiffusion in Polycrystalline Cubic C‐Type Yttria–Zirconia–Hafnia Solid Solutions

Cation inter diffusion in cubic C‐type solid solutions was investigated for the polycrystalline systems Y2O3—ZrxHf1‐x‐1O2 and Y2O3–ZrO2 in the small‐grain, deep‐penetration condition at 1615° to 1822°C. Lattice and grain‐boundary diffusion parameters were calculated from cation concentration distributions by using Oishi and Ichimura's grain‐boundary diffusion equation. The results indicated that Zr–Y and Zr–Hf interdiffusion coefficients decreased with an increase in Y content. The cation diffusivities were lower than anion diffusivities, and the interdiffusion parameters were lower in the C‐type cubic than in fluorite‐type cubic solid solutions. The results were compared with diffusivities in other C‐type cubic oxides.

Comparative aes studies of Cu diffusion through thin evaporated and ion-plated AgSn films

The process of grain boundary (GB) diffusion through thin evaporated and ion-plated Ag and AgSn films of 500 nm thickness was studied in the temperature range of about 150–250°C. Two methods were independently used for determination of the GB diffusion parameters: the so-called first appearance method and the simplified accumulation method. The values of activation energies and diffusivities have been determined from the Arrhenius plots. The change of activation energy and diffusivity with Sn concentration was explained by possible changes of thermodynamical properties of the samples occurring during GB diffusion.

Zr-Hf interdiffusion in polycrystalline Y2O3-(Zr+Hf)O2

Lattice and grain-boundary interdiffusion coefficients were calculated from the concentration distributions determined for Zr-Hf interdiffusion in polycrystalline 16Y2O3·84(Zr1−x Hfx)O2 withx=0.020 and 0.100. The lattice interdiffusion coefficients were described byD=0.031 exp [−391 (kJ mol−1)/RT] cm2 sec−1 and the grain-boundary diffusion parameters byσD′=1.5×10−6exp [−309(kJ mol−1)/RT] cm3 sec−1 in the temperature range 1584–2116° C. Comparison of the results with those for the systems CaO-(Zr+Hf)O2 and MgO-(Zr+Hf)O2 indicated that the Zr self-diffusion coefficient was insensitive to the dopants in the fluorite-cubic ZrO2 solid solutions.