Structure of binary antimony phosphate glasses by diffraction methods

Antimony phosphate glasses (Sb$_2$O$_3$)x(P$_2$O$_5$)$_1-x$ with $x$ = 0.05 and 0.80 were measured by neutron and X-ray diffraction with high real-space resolution. The P−O and O−O distance peaks of the PO$_4$ tetrahedra were found with the expected parameters. For the glass of $x$ = 0.80 the Sb−O and O−O coordination numbers and distances suggest highly distorted SbO$_3$ and SbO$_4$ environments according to strong lone-pair effects of the Sb$³⁺$. The fraction of SbO$_4$ has the right portion that all oxygens can form Sb−O−Sb or Sb−O−P bridges. Significant numbers of secondary Sb−O bonds (> 0.25 nm) are extracted. The first diffraction peak at 13 nm$⁻¹$ is related to distances between stacked layers of corner-connected oxygen triangles as in the orthorhombic Sb$_2$O$_3$. For the glass of $x$ = 0.05 the medium-range order reminds that of vitreous P$_2$O$_5$. Its SbO$_4$ units are formed with mean Sb−O bonds of 0.210 nm.