Novel KTP-like complex phosphates KMII0.33Nb0.67PO5 (MII—Mn, Co)

Single crystals of KTP-related phosphates of general formula KMII0.33Nb0.67PO5 (MII—Co, Mn) have been obtained in the pseudo-binary system K2Mo2O7–KMII0.33Nb0.67PO5 by means of the flux technique. The compounds have been studied by single crystal and powder X-ray diffraction, FTIR and UV–VIS spectroscopy. Both complex phosphates belong to the tetragonal system and crystallize in the enantiomorphous polar space groups P41 and P43. The structure contains cis-like helical chains which are connected by corner sharing Nb(MII)O6 octahedra and further linked through the PO4 tetrahedra. The potassium cations are located in the channels running along [001] direction of the anionic framework [MII0.33Nb0.67PO5]− and are irregularly coordinated by eight oxygen atoms. Potassium atom site is split into two equally occupied positions with q=0.5.