title: The atomic structure of niobium and tantalum containing borophosphate glasses.
abstract: A complete structural study has been carried out on sodium borophosphate glass containing increasing amounts of either niobium or tantalum. A combination of high energy x-ray diffraction, neutron diffraction, extended x-ray absorption fine structure, nuclear magnetic resonance, and infrared and Raman spectroscopy has been used to discern the local atomic structure of each component and the changes with M content, where M is either niobium or tantalum. The glasses are found to consist of tetrahedral borate and phosphate with octahedral MO(6). As expected, B and P play the roles of tetrahedral network formers. At low M content there are isolated MO(6) units with [Formula: see text] and [Formula: see text] linkages that contribute to the glass network. As the M content increases, the number of [Formula: see text] links increases, and at the highest M content each MO(6) unit is connected to several others. The octahedra become significantly distorted as the niobium content increases, an effect that is not seen for tantalum.
authors.affiliation: School of Physical Sciences, University of Kent, Ingram Building, Canterbury CT2 7NH, UK.
authors.forename: K M
authors.initials: KM
authors.lastname: Wetherall
authors.forename: P
authors.initials: P
authors.lastname: Doughty
authors.forename: G
authors.initials: G
authors.lastname: Mountjoy
authors.forename: M
authors.initials: M
authors.lastname: Bettinelli
authors.forename: A
authors.initials: A
authors.lastname: Speghini
authors.forename: M F
authors.initials: MF
authors.lastname: Casula
authors.forename: F
authors.initials: F
authors.lastname: Cesare-Marincola
authors.forename: E
authors.initials: E
authors.lastname: Locci
authors.forename: R J
authors.initials: RJ
authors.lastname: Newport