“…Several divalent including 3d metals, namely, Mn, Co, Fe, Zn, Cu, and Ni, are known to form the singlemetal cyclotetraphosphate M 2 P 4 O 12 , where M (II) stands for a divalent metal. The binary metal cyclotetraphosphates M 2−x A x P 4 O 12 (M and A=Mg, Ca, Mn, Co, Ni, Zn, or Cu; x=0-2), isostructural with the single metal cyclotetraphosphates M 2 P 4 O 12 , were prepared by Trojan et al [5][6][7][8] and Boonchomet al [9][10][11]. All these compounds have similarX-ray diffraction patterns and close unit cell parameters, which crystallize in monoclinic space group C2/c (Z=4) [12].…”