FERRISILICATE FELDSPARS AND FELDSPATOIDS - SYNTHESIS, X-RAY AND MOSSBAUER STUDY

Ferrisilicate analogous of monoclinic and triclinic potassium and rubi dium feldspars (KFeSi3O8 and RbFeSi3O8), potassium and rubidium leucit es (KFeSi2O6 and RbFeSi2O6), pollucite (CsFeSi2O6), (K,Rb,Cs)-ferrisil icates of kalsilite group (KFeSiO4, RbFeSiO4, and CsFeSiO4) were synth esized and studied with X-ray and Mossbauer methods. Unit cell paramet ers were refined and hyperfine parameters of Mossbauer spectra were de termined. Quadrupole shift epsilon proved to be more sensitive to the arrangement of the first coordination sphere than isomer shift delta. The former varies within the interval 0.1-0.3 mm/s whereas the latter - within 0.20-0.23 mm/s. Isomer shift increases for Cs-ferrisilicates as compared to that of (K,Rb)-ferrisilicates. Isomer shift increases w ith Fe,Si-ordering of these ferrisilicates.