Characterization and electronic properties of transition-metal exchanged zirconium and titanium phosphate

Abstract

A series of transition-metal-ion forms of phosphates of quadrivalent elements having the general formula X^[IV]M(PO4)2*yH2O(S^[IV] = Zr or Ti; M = Cu(II), Co(II) and Ni(II)) have been characterized. The electronic absorption spectra and magnetic moments of the copper, cobalt and nickel species indicate the presence of an octahedral stereochemistry (tetragonally distorted in the case of copper). Dehydration of the exchangers and phase transformations were studied using thermal and X-ray powder techniques. Electronic spectra and magnetic moments determined on the anhydrous and double phosphate phases indicate a decrease in coordination number from 6 to 4 with the formation of distorted tetrahedral structures. The sites within the a-zirconium phosphate cavity available to the hydrated transition-metal ions are discussed and a bonding scheme proposed based on stereochemistry of the ions.