Structure of Ba-Ti-Al-O glasses produced by aerodynamic levitation and laser heating

Abstract

Ba 0.09 Al 0.18 Ti 0.12 O 0.61 glasses have been produced by aerodynamic levitation and laser heating. Neutron diffraction, x-ray diffraction, x-ray absorption spectroscopy, molecular dynamics simulation, and reverse Monte Carlo refinement methods have been used to obtain a detailed atomistic structural model of the glass. This model has been used to investigate its atomic coordination and network structure. It is found that the Al atoms are almost exclusively fourfold tetrahedrally coordinated to oxygen atoms. In contrast, the Ti atoms coordinate to oxygen atoms in approximately equal numbers of four-and fivefold coordinated sites with a small number of sixfold sites. The results show the presence of some tetrahedral TiO 4 structural motifs although the dominant O-Ti-O bond angle occurs at 90• . It is found that Al/Ti-O network structure shows strong similarities with other oxide glass forming systems although a first sharp diffraction peak is not observed. The results are used to discuss the unusual properties of the Ba-Al-Ti-O glasses produced under different quenching conditions.

A Comparison of Structural Models of Tb3Al5O12 and Nd3Al5O12 Glasses Obtained When Using X-ray Data Alone and When X-ray and Neutron Data are Combined

“…Figure 2 shows the partial structure factor weightings for neutron scattering experiments. In contrast to the X-ray case it can be seen that the weighting of 12 may be clearly noted and support the observation previously that the Morse potentials of Pedone et al [16] are better for these aluminate glass systems [17]. data.…”

“…Previous studies[17] have suggested that the Morse potentials give a better initial agreement with the data than the Buckingham potentials.However, suitable Morse potentials forTb-O could not be found in the literature so we have used the Morse potentials of Pedone et al[16] for the…”

“…Hence, in the case of The network structure may be explored further by considering the Bhatia-Thornton Structure factors for the Al-O network as described in previous studies [8,17]. Figure 13 shows the results from the MD-RMC configurations of Finally, it is interesting to compare the refinement result for the case in which only the total X-ray and neutron diffraction patterns are used for the MD-RMC refinement.…”

Structure of liquid tricalcium aluminate

“…The low-r cutoffs used in the refinement were obtained by reference to the MD simulation. In addition, real-space data [ nat G(r)] was included to avoid a "pileup" of bonds close to the cutoff distances, primarily in g CaO (r) [38]. The mean square displacement from the original atoms at the end of the Fig.…”

Structural investigation of gallate glass using L3-edge extended X-ray absorption spectroscopy and computer simulation

“…To the best of our knowledge, several techniques such as Reverse Monte Carlo (RMC) [9] and Empirical Potential Structural Refinement (EPSR) [10] have been recently developed to obtain structural models of glasses from diffraction data. An alternative approach to the gallate glasses is to use Molecular Dynamics (MD) simulation techniques [11,12] to produce distribution function or diffraction patterns that can be compared directly with the experimental data.…”