The structure of vitreous boron oxide
01 Aug 1970-Journal of Applied Crystallography (International Union of Crystallography)-Vol. 3, Iss: 4, pp 251-257
TL;DR: In this article, a new study of the structure of vitreous boron oxide has been made under greatly improved conditions, using Rh Kα radiation with the method of fluorescence excitation, reliable intensity values were measured to 4πsinθ/λ = 20
Abstract: A new study of the structure of vitreous boron oxide has been made under greatly improved conditions. Using Rh Kα radiation with the method of fluorescence excitation, reliable intensity values were measured to 4πsinθ/λ = 20 A−1, and a rigorous interpretation was obtained in terms of pair functions. Each boron is triangularly surrounded by 3 oxygen atoms with a B–O distance of 1.37 A. Each oxygen atom is bonded to 2 boron atoms. The major part of the glass is made up of boroxol groups B3O6 (a hexagonal ring of 3 boron atoms and 3 oxygen atoms with 3 corner oxygen atoms outside the ring). These groups are linked together by sharing the corner oxygen atoms, with randomness in orientation about the B–O bond directions at the shared oxygen atoms. Within the ring the B–O–B angle is 120° and at the shared oxygen it is approximately 130°. There is satisfactory agreement between the calculated and measured pair function distribution curves. In vitreous B2O3 the scheme of bonding does not fill space, and any boroxol group has neighboring groups which are not directly connected to it by B–O and O–B bonds. The measured pair function areas indicate neutral atoms, so that the bonding is predominantly covalent.
Citations
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TL;DR: Lipson and Steeple as mentioned in this paper interpreted X-ray powder diffraction patterns and found that powder-diffraction patterns can be represented by a set of 3-dimensional planes.
Abstract: Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.
1,867 citations
TL;DR: In this paper, the Krogh-Moe hypothesis was used to identify the structural groups present in the borate on the basis of Raman spectroscopic measurements in borate glasses.
Abstract: Raman spectroscopic measurements in borate glasses have been reviewe. The review shows that the technique is useful in identifying the structural groups present in the borate on the basis of the Krogh-Moe hypothesis. Vitreous B2O3 and alkali borates are extensvvely studied and a satisfactory assignment of bands is possible by a careful consideration of the literature. A cation effect on the borate netwoork is observed. Availaable measurements on binary borates other than alkali borates and on ternary borates are limited and more work is required to identify the structural modifications that take place with composition. Mixed alkali effect is reported only lithium-caesium borade and shows the formation of non-bridging oxygens, destroying the six-membered rings when Li2O is replaced by Cs2O. Fast ionic glasses (alkali borates containing alkali halides) yield the same Raman spectra as the alkali borates, except when the alkali is a fluoride.
355 citations
TL;DR: This paper presents a two-state statistical mechanical model of boron speciation in which addition of network modifiers leads to a competition between the formation of nonbridging oxygen and the conversion ofboron from trigonal to tetrahedral configuration, and derives a detailed topological representation of alkali-alkaline earth-borosilicate glasses that enables the accurate prediction of properties such as glass transition temperature, liquid fragility, and hardness.
Abstract: Borosilicate glasses display a rich complexity of chemical behavior depending on the details of their composition and thermal history. Noted for their high chemical durability and thermal shock resistance, borosilicate glasses have found a variety of important uses from common household and laboratory glassware to high-tech applications such as liquid crystal displays. In this paper, we investigate the topological principles of borosilicate glass chemistry covering the extremes from pure borate to pure silicate end members. Based on NMR measurements, we present a two-state statistical mechanical model of boron speciation in which addition of network modifiers leads to a competition between the formation of nonbridging oxygen and the conversion of boron from trigonal to tetrahedral configuration. Using this model, we derive a detailed topological representation of alkali–alkaline earth–borosilicate glasses that enables the accurate prediction of properties such as glass transition temperature, liquid fragi...
287 citations
TL;DR: Raman spectra of alkali and alkaline earth borosilicate glasses were used to discuss the molecular structure of the glasses and the influence of Al 2 O 3 additions on the structure of borosile glass is also discussed as mentioned in this paper.
Abstract: Raman spectra of alkali and alkaline earth borosilicate glasses are reported. These spectra are used to discuss the molecular structure of the glasses. The influence of Al 2 O 3 additions on the structure of borosilicate glass is also discussed. It is shown that the same type of groups are present in borosilicate glasses as in borate and silicate glasses. The presence of large borate groups such as tetraborate and metaborate groups is strongly suggested by the Raman spectra. It appears that boron ions are hardly taken up in the silicon-oxygen network. Our results suggest that the region of phase separation is larger than the region presently acknowledged.
237 citations
TL;DR: In this article, the effect of PbO on the borate network was studied by Raman spectroscopy with a view to understand the effect on boroxol rings in the form of pentaborate and diborate units.
Abstract: Glasses in the system $xPbO:(100- x)B_2O_3 (22\leq x\leq 85$ mol%) have been studied by Raman spectroscopy with a view to understand the effect of PbO on the borate network. The conversion of three-fold to four-fold coordinated boron takes place primanly by incorporation of $BO_4$ into boroxol rings in the form of pentaborate and diborate units. For high lead content, back conversmn of four to three coordinatmn of borons occurs and the network consists primardy of pyroborate, orthoborate and metaborate groups.
235 citations
References
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[...]
TL;DR: Lipson and Steeple as mentioned in this paper interpreted X-ray powder diffraction patterns and found that powder-diffraction patterns can be represented by a set of 3-dimensional planes.
Abstract: Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.
1,867 citations