Structural and optical properties of lithium bismuthate glasses
- PDF / 107,011 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 49 Downloads / 199 Views
Structural and optical properties of ion-conducting lithium bismuthate glasses are reported here. The structure of these glasses has been explored from the compositional variation of the density, molar volume, and glass transition temperature. The optical study in the visible and infrared region indicates a large transmission window for these glasses. The BiO6 octahedra were identified as the main structural unit from the Raman spectra of these bismuthate glasses.
I. INTRODUCTION
A considerable attention has been paid for a few decades to study the properties of ionic glasses formed with glass formers such as SiO2, P2O5, B2O3, TeO2, etc. The local structure of sodium in a glassy silicate network was explored using EXAFS.1 The modified random network model was proposed to explain the ion dynamics in these glasses.2,3 It was observed that the introduction of metal oxides in phosphate glasses leads to a depolymerization of the P–O–P network,4 which was confirmed by 31 P MASNMR. 5,6 X-ray photoelectron spectroscopy analysis was used to determine the ratio of the bridging oxygen to the terminal sites for phosphate glasses.6 –8 The NMR,9–13 Raman,14,15 Infrared (IR) absorption,11,16 neutron diffraction,17 etc., results supported that the introduction of a network modifier in borate glasses resulted in a progressive increase in the number of four-coordinated boron atoms at the expense of threecoordinated boron atoms. Krogh-Moe18 explored the structural change in sodium and lithium borate glasses by assuming the network in the short-range order to be built up of the same structural units as those existed in the crystalline counterparts. In the case of tellurite glasses, earlier x-ray diffraction (XRD) studies19,20 revealed a coordination number for tellurium atom as 6. The IR study of the tellurite glasses and the polycrystalline compounds confirmed the analogy in the short-range order between vitreous and crystalline counterparts.21 The neutron diffraction studies22 of tellurite glasses contradict the earlier XRD studies and asserted the coordination number of tellurium as 4. The Raman study23 of binary
a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 8, Aug 2002
http://journals.cambridge.org
Downloaded: 19 Apr 2015
alkali-metal tellurite glasses and their crystalline counterparts indicated a change in the coordination of the tellurium atom from TeO4 trigonal bipyramids through TeO3+1 polyhedra to TeO3 trigonal pyramids. However, the study of the physical properties of the ionic glasses formed with a heavy metal oxide such as Bi2O3 has been paid little attention. These glasses are interesting from the application point of view as they can be used as layers for optical and optoelectronic devices, thermal and mechanical sensors, reflecting windows, etc.24 – 29 Recent structural studies of lithium alkaline earth bismuthate glasses30 showed the presence of distorted BiO6 octahedra as the main structural unit. At lower Li2O content, Li+ ions go into the struct
Data Loading...
