Structural studies on molten glasses by an X-ray anomalous scattering

In recent years，great attention has been paid to“non-conventional glasses”which do not vitrify by themselves but do vitrify on addition of second components。Therefore，these glasses are expected to have properties very different from conventional glasses such as SiO_2and B_2O_3.In the present study，we focused especially on gallate glasses as nonconventinal glasses.The structure of 4ONa_2O_3·20Ga_2O_3·40TiO_2glass was investigated on terms of X-ray dadial distribution function(RDF)method。As a result，it was revealed that the unit structure of both Ti^&lt；4&gt；and Ga^&lt；3&gt；is tetrahedrally four fold-coordinated in the glass.This result is largely different from the one for the Na_2O·2TiO_2glass in which TiO_4tetrahedra and TiO_6octahedra coexist。This fact clearly explains the difference in glass formation tendency between the above two glasses that the former glass easily vitrify while the latter does not。The Ti-O bondlength also explains this fact.That is，the bondlengths…More of Ti-O and Ga-O are 0.186 nm in the 40Na_2O·20Ga_2O_3·40TiO_2glass，while that of Ti-O in the Na_2O·2TiO_2glass is 0.199 nm which is considerably longer compared to the former case.Next，the structure of 50PbO·5OGaO_&lt；1.5&gt；and 80BiO_&lt；1.5&gt；·20GaO_&lt；1.5&gt；glasses were fully investigated by the neutron and X-ray analyzes.glassIn both glasses，Ga^&lt；3&gt；is tetrahedrally coordinated。Pb^&lt；2&gt；in the50PbO·5OGaO_&lt；1.5&gt；glass forms chains consisting of PbO_3trigonal pyramids and/or PbO_4tetragonal pyramids as found in the PbSiO_3alamosite crystal.That is，Pb^&lt；2&gt；acts as the glass-network former。Contrarily to this，Bi^&lt；3&gt；in the 80BiO_&lt；1.5&gt；·20GaO_&lt；1.5&gt；takes the coordination states of BiO_5and/or BiO_6foming(BiO_5，BiO_6)_n sheets.Moreover，the V_2O_5-P_2O_5glasses with different amounts of V^&lt；4&gt；were studied on the structure by the X-ray diffraction method。It is found that V^&lt；5&gt；in the glasses are present in the coordination states of both VO_5trigonal bipyramids and VO_3tetrahedra.With the use of the solid state detector(SSD)for X-ray introduced in the present study，it has become possible to measure the more precise of glasses in a shorter time，making it possible to analyze the complicated structure of glasses with ease.Less：Less

In recent years, great attention has been paid to "non-conventional glasses" which do not vitrify by themselves but do vitrify on addition of second components. Therefore, these glasses are expected to have properties very different from conventional glasses such as SiO_2 and B_2O_3. In the present study, we focused especially on gallate glasses as nonconventinal glasses. The structure of 4ONa_2O_3・20Ga_2O_3・40TiO_2 glass was investigated on terms of X-ray dadial distribution function (RDF) method. As a result, it was revealed that the unit structure of both Ti^<4+> and Ga^<3+> is tetrahedrally four fold-coordinated in the glass. This result is largely different from the one for the Na_2O・2TiO_2 glass in which TiO_4 tetrahedra and TiO_6 octahedra coexist. This fact clearly explains the difference in glass formation tendency between the above two glasses that the former glass easily vitrify while the latter does not. The Ti-O bondlength also explains this fact. That is, the bondlengths … More of Ti-O and Ga-O are 0.186 nm in the 40Na_2O・20Ga_2O_3・40TiO_2 glass, while that of Ti-O in the Na_2O・2TiO_2 glass is 0.199 nm which is considerably longer compared to the former case.Next, the structure of 50PbO・5OGaO_<1.5> and 80BiO_<1.5>・20GaO_<1.5> glasses were fully investigated by the neutron and X-ray RDF analyzes. In both glasses, Ga^<3+> is tetrahedrally coordinated. Pb^<2+> in the 50PbO・5OGaO_<1.5> glass forms chains consisting of PbO_3 trigonal pyramids and/or PbO_4 tetragonal pyramids as found in the PbSiO_3 alamosite crystal. That is, Pb^<2+> acts as the glass-network former. Contrarily to this, Bi^<3+> in the 80BiO_<1.5>・20GaO_<1.5> takes the coordination states of BiO_5 and/or BiO_6 foming (BiO_5 , BiO_6) _n sheets.Moreover, the V_2O_5-P_2O_5 glasses with different amounts of V^<4+> were studied on the structure by the X-ray diffraction method. It is found that V^<5+> in the glasses are present in the coordination states of both VO_5 trigonal bipyramids and VO_3 tetrahedra.With the use of the solid state detector (SSD) for X-ray introduced in the present study, it has become possible to measure the more precise RDF of glasses in a shorter time, making it possible to analyze the complicated structure of glasses with ease. Less