A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses

Abstract Diffraction experiments were performed on two (Nd2O3)x(P2O5)1- x glasses for studying the en­ vironmental order of the Nd3+ 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 (OT) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all OT's are in N d-OT-P positions. In the metaphosphate glass the NdOn polyhedra have to share some OT sites.