The influence of some transition metal ions in lead- and calcium-phosphate glasses

Highlights: ► Preparation of phosphate glasses dopped with: CuO, V2O5, Fe2O3, MoO3. ► EPR investigation on x(CuO·V2O5)(100−x)[P2O5·CaO] glass system, x ⩽ 50 mol%. ► EPR investigation on x(Fe2O3MoO3) (1−x)[2P2O5PbO] glass system, x ⩽ 50 mol%. - Abstract: Phosphate glasses, despite of their poor chemical durability have many biomedical and technological applications. Phosphate materials containing calcium oxide are intensely studied because they may have bioactive potential. Such materials with calcium oxide can be produced to have similar bone structure or to be used as microstructures for active implant. On the other hand phosphate materials containing lead oxide are used in the nuclear technique as nuclear waste encapsulation. The present work is a structural study on some phosphate glasses containing vanadium, copper, molybdenum and iron ions. The following two glass systems were investigated by EPR method: x(CuO·V2O5)(100−x)[P2O5·CaO] and x(Fe2O3MoO3) (1−x)[2P2O5PbO] with 0.5 ⩽ x ⩽ 50 mol%. In both systems, EPR spectra evidenced the hyperfine structure of vanadium and molybdenum ions. EPR parameters indicate the presence of V4+ ions in C4V symmetry until 7 mol%. After this concentration the hyperfine structure of vanadium disappears due to the clusters formation. Hyperfine structure of copper was not evidenced in x(CuO·V2O5)(100−x)[P2O5·CaO] system. EPR spectra for xFe2O3MoO3 (1−x)[2P2O5PbO] evidence the presence of molybdenum ions in a C4v symmetry, but for iron ions weak signals at g ≈ 6.91 and g ≈ 4.24 appear suggesting the presence of isolated Fe3+ ions. For x ⩽ 5 mol% these two signals disappear suggesting also the clusters formation. Glasses containing simultaneous two types of paramagnetic ions evidence the presence of mixed ion pairs (Cu2+–V4+, Mo5+–Fe3+) which improve magnetic properties of the studied glasses.