A neutron and x-ray diffraction study of the structure of Nd phosphate glasses

Abstract

<jats:title>Abstract</jats:title> <jats:p> Diffraction experiments were performed on two (Nd<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>)<jats:sub>x</jats:sub>(P<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>)<jats:sub>1- x</jats:sub> glasses for studying the en­ vironmental order of the Nd<jats:sup>3+</jats:sup> cations. In case of the metaphosphate glass (x = 0.25) a combination of X-ray and neutron diffraction data was used to separate the Nd-O and O-O first neighbor peaks. An Nd-O coordination number of 6.6±0.3 and a mean Nd-O distance of (0.239±0.001) nm were determined. In the ultraphosphate glass studied (x = 0.20) these values increase to 6.9±0.3 and (0.240±0.001) nm where the Nd-0 coordination number is equal to the number of terminal oxygen atoms (O<jats:sub>T</jats:sub>) which are available for coordination of each Nd<jats:sup>3+</jats:sup> cation. This indicates the formation of NdO<jats:sub>n</jats:sub> polyhedra not sharing any O atom where also all O<jats:sub>T</jats:sub>'s are in N d-O<jats:sub>T</jats:sub>-P positions. In the metaphosphate glass the NdO<jats:sub>n</jats:sub> polyhedra have to share some O<jats:sub>T</jats:sub> sites.</jats:p>