Powder x-ray diffraction has been used to search for effects that indicate the influence of ionic KCN nanocrystals embedded in the ionic compound KI by measuring Bragg reflections of the matrix. Due to the extremely slow phase separation processes on the time scale of months it was necessary to perform measurements in several periods. At first the boundary between solid solutions of KCN in KI and the mixture of the two crystalline compounds has been determined. Finally, a splitting of diffraction peaks has been observed in a powder sample made from an optically homogeneous large single crystal containing a small excess of KCN. The splitting is traced back to elastic forces acting at the interface between embedded KCN-rich nanocrystals and the surrounding matrix. In contrast to piezoelectric nanocrystals the elastic continuum theory is working quantitatively in the ionic system $\mathrm{K}\mathrm{C}\mathrm{N}\mathrm{K}\mathrm{I}$.

• Received 20 December 2004

DOI:https://doi.org/10.1103/PhysRevB.72.045432