Kinetic instability of multicomponent solids in generalized thermodynamic gradients

Abstract

In general, multicomponent solids at high temperatures are unstable in gradients of temperature, pressure, and chemical potential. The instability arises from differences in the transport coefficiencies of the components. Recent examples of the phenomenon are discussed. Homogeneous solid solutions can undergo demixing, and stoichiometric compounds can decompose in isothermal chemical potential gradients. In addition, there is a shift of the sample in the direction of increasing chemical potential and morphological instability at the lower chemical potential boundary. A quantitative treatment within the Onsager regime of irreversible thermodynamic is presented. The occurrence of kinetic instability can limit applications of ceramics in high-temp. technology.