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. 1. Introduction Orthophosphoric acid condenses to diphosphoric acid under heat treatment. The related salts are called diphosphates (pyrophosphates), which contain P2O7 groups, for example, copper hydroxydiphosphate Cu3[P2O6OH]2 [1] and copper pyrophosphate α-Cu2P2O7 [2]. Further condensation in the presence of cations leads to polyphosphates (short chains) or metaphosphates. Two kinds of metaphosphates, the catena phosphates with 2-corner-linked PO4 tetrahedra (infinite chains of Q2 units) and the cyclophosphates (rings of Q2 units), have to be distinguished. In comparison to that, ultraphosphates show linked together Q2 and Q3 (2- and 3-corner-linked PO4 tetrahedra) and build layer or chain structures. Basically, it is differentiated between nonbonded (Q0) monophosphates, primary bonded (Q1) diphosphates, secondary bonded (Q2) meta- and cyclophosphates, and tertiary bonded (Q3) framework phosphates (pure P2O5). Polyphosphates and ultraphosphates are mixed structures (Q1 and Q2, resp., Q2 and Q3) of different bonded structural (PO4) units [3–5]. The copper ion in the copper phosphates is regularly coordinated with four, five, or six oxygen atoms, but most structures consist of tetrahedral or octahedral CuO groups. About twenty different structures of copper phosphates have been discovered to date. The larger family is that of copper monophosphates, which shows a molar ratio of Cu/P = 1. The new structure of CuHPO4 does belong to this group [3]. The copper polyphosphates with a molar ratio of Cu/P < 1 are much less numerous, for example, the
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