Crystal structures of new layered perovskite-type oxyfluorides, CsANb2O6F (A = Sr and Ca) and comparison with pyrochlore-type CsNb2O5F

Layered perovskite-type, oxyfluorides CsANb2O6F (A = Sr and Ca) and 3-D pyrochlore-type CsNb2O5F were synthesized and characterized by synchrotron X-ray diffraction data. The structural distortion evaluated by the Nb-O(F) bond angle shows a good correlation with the optical band gap.142