The structural role of manganese ions in some zinc phosphate glasses and glass ceramics

X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy measurements have been employed to investigate the samples from the (MnO)x·(P2O5)40·(ZnO)60−x (0 ≤ x ≤ 30 mol%) system. The samples had a fixed P2O5 content of 40 mol% and the MnO:ZnO ratio was varied. The XRD pattern for the prepared samples shows that the vitreous phase is present only for x ≤ 20 mol%. For the sample containing 30 mol% MnO the presence of a crystalline phase was evidenced, namely the manganese phosphate (Mn2P2O7) embedded in an amorphous matrix. In this case the XRD patterns show the presence of nanometer crystals (56 nm) in a glassy matrix. The estimated amount of the crystalline phase was 74%. The electron micrographs show the structural evolution of the studied samples from a completely amorphous state (for the samples up to 20 mol% MnO) to a partly crystalline one (for the sample with 30 mol% MnO). FTIR data revealed that the short-range order of the glassy matrix is affected by the addition of the MnO to the (P2O5)40·(ZnO)60 host glass matrix. The compositional dependence of the different structural units which appear in the studied samples was followed. FTIR spectroscopy data suggest that the manganese ions play the network modifier role in the studied samples.