| | 1 | Author
| Uwe Hoppe, Rainer Kranold, Dörte Stachel, Andrea Barz, AlexC. Hannon | Requires cookie* | | | Title
| Variation in P-O Bonding in Phosphate Glasses -A Neutron Diffraction Study  | | | | Abstract
| Two different lengths of P-0 bonds in the P0 4 units of phosphate glasses are found by neutron diffraction experiments of high resolution in real space. The two lengths are related to bonds of the phosphorus atom with the terminal and the bridging oxygen atoms. The mean lengths and widths of both P-0 distance peaks change as a function of the glass composition. In a large range, starting from vitreous P 2 O s up to the pyrophosphate composition, the behavior of the bond lengths is compared with that in the related crystals and with that resulting from ab initio calculations. The bond lengths depend not only on the species of the participating oxygen atoms and on the number of links of the concerning P0 4 unit but also on the number of links of the neighboring P0 4 unit and on the species of the modifier cation. | | | |
Reference
| Z. Naturforsch. 55a, 369—380 (2000); received October 6 1998 | | | |
Published
| 2000 | | | |
Keywords
| Neutron Diffraction, Short-range Order, Phosphate Glasses | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/55/ZNA-2000-55a-0369.pdf | | | | Identifier
| ZNA-2000-55a-0369 | | | | Volume
| 55 | |
| 2 | Author
| Uwe Hoppe3, Günter Walter8, Dörte Stachelb, AlexC. Hannonc | Requires cookie* | | | Title
| S | | | | Abstract
| h o r t-R a n g e O r d e r D e ta ils o f M e ta p h o s p h a te G la s s e s S tu d ie d b y P u ls e d N e u tr o n S c a tte r in g Details of the short-range order of the binary metaphosphate glasses A1P30 9 and PbP2Oe and the ternary glass system ZnO-MgO-2P2Os have been studied by pulsed neutron scattering which provides a measuring range up to about ß m ax = 500 nm-1. The splitting of the P-O peak in the distance correlation functions attributable to the different bond lengths for the non-bridging and bridging oxygens was found to decrease with increasing field strength of the network-modifier cations. For the ternary system ZnO-MgO-2P2Os the peak in the distance correlation function, T(r), produced by the first oxygen neighbours around Zn2+ and Mg2+ was separated by the additional use of the X-ray structure factor. The distances rZn0 and rM gQ extracted from the separated peaks are slightly different from those obtained from the binary glasses ZnP20 6 and MgP20 6. The metal-oxygen coordination numbers were found to be NZn0=4.5 and NM g0 = 5.5. For the two binary systems the coordination numbers Al-0 and Pb-0 were obtained to be 7 and 5, respectively. | | | |
Reference
| Z. Naturforsch. 50a, 684—692 (1995); received March 6 1995 | | | |
Published
| 1995 | | | |
Keywords
| Pulsed neutron scattering, phosphate glasses, short-range order | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/50/ZNA-1995-50a-0684.pdf | | | | Identifier
| ZNA-1995-50a-0684 | | | | Volume
| 50 | |
| 3 | Author
| Z. Naturforsch | Requires cookie* | | | Title
| A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses | | | | Abstract
| Diffraction experiments were performed on two (Nd203)x(P205)i_ 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 N d-0 and 0 -0 first neighbor peaks. An N d-0 coordination number of 6.6±0.3 and a mean N d-0 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 N d-0 coordination number is equal to the number of terminal oxygen atoms (0 T) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all 0 T's are in N d-0T-P positions. In the metaphosphate glass the NdO" polyhedra have to share some 0 T sites. | | | |
Reference
| Z. Naturforsch. 56a, 237—243 (2001); received January 8 2001 | | | |
Published
| 2001 | | | |
Keywords
| Neutron Scattering, X-ray Scattering, Short-range Order, Phosphate Glasses | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/56/ZNA-2001-56a-0237.pdf | | | | Identifier
| ZNA-2001-56a-0237 | | | | Volume
| 56 | |
| 4 | Author
| E. Sváb, F. Hajdu, Gy Mészáros | Requires cookie* | | | Title
| S | | | | Abstract
| e m i-E m p iric a l F ittin g o f P a r t i a l P a i r C o r r e la tio n F u n c tio n s o f A m o rp h o u s A llo y s A semi-empirical fitting procedure has been developed and used in analysing the characteristic features of the partial structure factors of binary amorphous alloys. An analytical formula is given to fit the experimental atomic pair correlation function as a sum of Gaussians. The inverse Fourier transform of the fitted terms reproduces all features of the experimental structure function. In addition to the structural parameters, the modelling gives a quantitative explanation for the complex origin of characteristic features in the diffraction pattern such as pre-peak, pre-minimum, and split peaks in the partial structure factor. | | | |
Reference
| Z. Naturforsch. 50a, 1205—1210 (1995); received September 22 1995 | | | |
Published
| 1995 | | | |
Keywords
| Metallic glass, Short range order, Partial correlations, Neutron diffraction, Fitting | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/50/ZNA-1995-50a-1205.pdf | | | | Identifier
| ZNA-1995-50a-1205 | | | | Volume
| 50 | |
| 5 | Author
| Uwe Hoppe, Günter Walter, Dörte Stachel, Andrea Barz, AlexC. Hannon | Requires cookie* | | | Title
| Neutron and X-ray Diffraction Study on the Structure of Ultraphosphate Glasses | | | | Abstract
| The high real-space resolution of neutron diffraction experiments which is provided by use of the epithermal neutrons from spallation sources was exploited in order to differentiate the unlike P-O bonds existing in the P0 4 units of phosphate glass networks. The 2 P-O distance peaks, separated by about 12 pm, which were found in the zinc and the calcium ultraphosphate glasses studied are assigned to oxygen sites on bridging (O b) and terminal (O X) positions. The mean P-O distances are nearly invariable versus the growing metal oxide content which results from an elongation of the P-O b and P-O t bonds. The bond lengths which are known from the related crystal structures and from ab initio calculations show almost the same behaviour. The discussion of further details of the crystal structures leads to the conclusion that P-O b rather than P-O t distances should show more details in case of diffraction measurements of even higher real-space resolution. The change of the Zn-O coordination number from 6 to 4 versus increasing ZnO content, which was obtained in previous X-ray diffraction experiments, is confirmed by the recent combination of neutron and X-ray diffraction data. On the other hand, the Ca-O coordination number of about 6 is almost invariable. | | | |
Reference
| Z. Naturforsch. 52a, 259—269 (1997); received July 6 1996 | | | |
Published
| 1997 | | | |
Keywords
| Neutron diffraction, X-ray diffraction, Phosphate glasses, Short-range order | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/52/ZNA-1997-52a-0259.pdf | | | | Identifier
| ZNA-1997-52a-0259 | | | | Volume
| 52 | |
| 7 | Author
| Uwe Hoppe, Günter Walter, Rainer Kranold, Dörte Stachel | Requires cookie* | | | Title
| An X-ray Diffraction Study of the Structure of Vitreous P2O5 | | | | Abstract
| Recently, the lengths of the two P-0 bonds in the P0 4 tetrahedron were obtained by neutron diffrac-tion of high real-space resolution. By use of the present X-ray diffraction experiments, the P-P distance belonging to pairs of corner-linked P0 4 units is determined. Using this length of (294 ± 2) pm and tak-ing into account the P-0 bond distance to the bridging oxygen atom of 158 pm, a mean P-O-P angle of 137° ± 3° is calculated. The reverse Monte Carlo simulations fit the neutron and X-ray structure fac-tors. The P-O-P angle distribution obtained this way possesses a mean angle of 141°. An interpretation of the first scattering peaks is presented by analysing the occupancy and the distances of various co-ordination shells by use of model configurations. The low occupancy of the first shells allows the ap-plication of the schematic hole model of Dixmier. The first X-ray diffraction peak at 13 nra" 1 is related to the P-P2nd shell, the shoulder at 20 nm -1 arises from the P-0 2nd shell. The most similar crystalline structure with vitreous P2O5 is the orthorhombic P2O5, form II. But it has more effectively orientated terminal oxygen atoms and, thus, a higher packing than the glass. | | | |
Reference
| Z. Naturforsch. 53a, 93—104 (1998); received December 22 1997 | | | |
Published
| 1998 | | | |
Keywords
| Vitreous P 2 0 5, X-ray Diffraction, Short-range Order, Reverse Monte Carlo | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/53/ZNA-1998-53a-0093.pdf | | | | Identifier
| ZNA-1998-53a-0093 | | | | Volume
| 53 | |
| 8 | Author
| G. Herms, J. Sakowski, W. Gerike, Dörte Stachel | Requires cookie* | | | Title
| Structural Changes in Two Different Types of Oxide Glass Melts: Borates and Metaphosphates | | | | Abstract
| X-ray diffraction experiments of molten oxide glasses, which give new insights into the structure of melts, were carried out. Using modern means (synchrotron radiation, image plates, container-less high-temperature technique) it could be shown that the short range order of melt and solid glass is often qual-itatively different. If vitreous B 2 0 3 or binary borate glasses with low content of network modifier are heated up above T & , the network topology begins to alter. With rising temperature more and more of the boroxol groups are replaced by independent B0 3 groups. While melting a metaphosphate glass, how-ever, structural changes of another kind take place. In solid glass the environment of the network mod-ifier ions is similar to the one found in crystalline modifications, and their distances to the surrounding P0 4 tetrahedra have narrow distributions. In the melt, however, these distances scarcely become evi-dent, probably owing to the increased thermal motion of the modifier ions. | | | |
Reference
| Z. Naturforsch. 53a, 874—882 (1998); received February 17 1997 | | | |
Published
| 1998 | | | |
Keywords
| X-ray Diffraction, Short Range Order, Borate Glasses, Phosphate Glasses, Glass Transition | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/53/ZNA-1998-53a-0874.pdf | | | | Identifier
| ZNA-1998-53a-0874 | | | | Volume
| 53 | |
|
