Diffusion in the System K2O‐SrO‐SiO2: III, Interdiffusion Coefficients*

Abstract
The matrix of interdiffusion coefficients, [D], was determined by measuring spatial composition distribution in couples with compositions (in wt fractions) near 0.21K2O‐0.17SrO‐0.62SiO2 after they were heat‐treated for various times at 630° to 810°C. The results are consistent with the Onsager hypothesis in that [D] at a given temperature is independent of diffusion time and the direction (in composition space) of the diffusion couple. The eigenvectors and eigenvalues of the [D] matrix were determined; the diffusion paths in composition space are thus easily understood. As is consistent with intuition, the “fast” eigenvector nearly parallels the direction of constant SiO2 concentration.