Distribution Of Phosphate Anions Research Articles

The structure and properties of xZnO–(67–x)SnO–33P2O5 glasses: (IV) Mechanical properties

The Vickers hardness, Young's modulus, and shear modulus of xZnO–(67–x)SnO–33P2O5 glasses increase with increasing values of x, in agreement with predictions that consider the quantitative structural information regarding coordination numbers of Zn2+ and Sn2+ ions by diffraction methods, and phosphate anion distributions by NMR methods, reported in an earlier study. The compositional dependence of the shear modulus falls into two ranges which correlate with trends in photoelasticity, and the elastic and photoelastic properties are explained considering changes in ion packing ratio and average bond strengths when ZnO replaces SnO.

The structure and properties of cesium loaded Mo-Fe-phosphate glasses

Chemically durable iron phosphate glasses are promising candidates for hosting nuclear wastes containing constituents like Cs2O and MoO3 that have lower solubility in more conventional borosilicate glasses. In this work, two series of Cs-Mo-Fe-phosphate glasses were prepared and characterized. For glasses in Series A (xCs2O∙(100-x)∙(15MoO3∙22.5Fe2O3∙62.5P2O5), x = 0, 7.5, 15.0, 22.5), increasing Cs2O contents increase the molar volume and decrease the glass transition temperature. Raman spectroscopy reveals that adding Cs2O breaks down linkages between MoO6 octahedra, replacing MoOMo and MoO bonds with Mo-O−Cs+ bonds. Phosphate anion chromatography reveals that adding Cs2O has little effect on the phosphate anion distributions. For glasses in Series B (15Cs2O∙ yMoO3∙(28.75-y)Fe2O3∙56.25P2O5, y = 0, 5.75, 11.50, 17.25, 23.00, 28.75), the glass transition temperature decreases and the aqueous dissolution rates increase when MoO3 replaces Fe2O3. The formation of isolated MoO6 octahedra with Mo-O−Cs+ bonds results in an increase in the average phosphate anion-length in the MoO3-rich glasses. Mössbauer spectroscopy indicates that ferric ions dominate in both series, and that the average Fe-coordination number increases with increasing Cs2O content (series A) and with increasing MoO3 content (series B).

The properties and structure of zinc magnesium phosphate glasses

Zn–Mg-phosphate (ZMP) glasses, including those with the nominal molar compositions (50−x)ZnO xMgO 50P2O5 (0≥x≥50) and (60−y)ZnO yMgO 40P2O5(0≥y≥60), were prepared and properties such as density, refractive index, coefficient of thermal expansion and glass transition temperature (Tg), were measured. The glass transition temperature increases by 100–150°C and the room temperature dissolution rates in water decrease by 1–2 orders of magnitude when MgO replaces ZnO while maintaining a constant P2O5 content. Glass structures were characterized by Raman spectroscopy and there were no significant changes in the phosphate anion distributions when MgO replaces ZnO. The significant changes in properties cannot be explained by a simple cation field strength argument since Mg2+ and Zn2+ have similar sizes; instead, the effect of 3d electrons on the nature of the bonds between Zn2+ ions and non-bridging oxygens on the phosphate tetrahedra must be considered.

Structure of zinc polyphosphate glasses

The technique of high-performance liquid chromatography (HPLC) has been used to determine the distributions of phosphate-anion chains and rings in a variety of zinc-phosphate-based glasses. The phosphate-anion distributions in simple binary zinc phosphate glasses are compared to those found in multi-cation alkali-zinc phosphate glasses. Multi-cation zinc phosphate glasses are chemically durable and can be tailored to exhibit transition temperatures sufficiently low for co-processing with a variety of plastics to form novel organic–inorganic composite materials. The intermediate range order in the multi-cation glasses is found to be similar to that measured in the binary zinc-phosphate glasses. Scanning calorimetry measurements indicate, however, that the multi-cation glasses are more resistant to crystallization than the binary glasses. The fraction of phosphorus sites with 2 ( Q 2), 1 ( Q 1) and 0 ( Q 0) bridging oxygen, as well as the ratio of bridging to non-bridging oxygen (BO/NBO), are obtained from the chromatograms. Structural data for the zinc phosphate glasses obtained using HPLC are compared to results reported in the literature that were deduced using more-traditional solid-state techniques such as NMR, XPS, and Raman spectroscopy.

Chromatographic Determination of the Phosphate Anions in Crystalline and Glassy Na4NbP3Oz

High-performance liquid chromatography (HPLC) measurements on crystalline and glassy Na4NbP3Oz prove that the crystalline phase is a pyrophosphate and that the glassy material contains a distribution of phosphate anions with anions up to five PO4 tetrahedra in length. Powder X-ray diffraction data for a new trimetaphosphate crystalline phase with the composition Na3NbP3Ox are also reported.