Modulated structures in melilites

Abstract

Many studies on melilite group have been carried out in these two decades, and two significant features of the materials have been clarified so far. A number of descriptive and synthetic studies of melilite group have revealed that the compounds are highly tolerant of accommodating various combinations of elements in the structure. Another feature is the incommensurate structure-modulation found in melilites containing Ca as a major element. Structural studies with X-ray diffraction data and a treatment in the five-dimensional space clarified that formation and ordered arrangements of the six-coordinated Ca atoms play an important role to stabilize the long-range order in the modulated structures.