Spectral Investigation of Crystalline (CuHPO4, Cu2P4O12, and Cu2P8O22) and Glassy Copper Phosphates

Abstract

Emerald green crystals of the new composition CuHPO4 were synthesized and compared to (copper metaphosphate) Cu2P4O12 and (copper ultraphosphate) Cu2P8O22. Various copper ultraphosphate and metaphosphate glasses of different compositions between pure P2O5 and Cu2P4O12 were melted in crucibles or in evacuated and sealed silica ampoules at 1473 K or 1373 K for 2 hrs. The UV-VIS-spectra and the IR-spectra of all crystals and glasses were measured and compared. The absorption band of Cu2+ was resolved into more component Gaussian bands and differentiated between square-pyramidal and octahedrally coordinated copper. These structural changes are responsible for colour changes from green to turquoise. The infrared spectroscopic properties of the copper phosphate glasses differ between metaphosphate and ultraphosphate structures but show similarities between the crystals and the glasses of the same structure type. EPR studies of some of the glasses show different kinds of spectra, with increasing copper content.