Browsing by Author "Komatsu T."
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Item Average single bond strength and optical basicity of Na2O- GeO2 glasses(2009-01-01) Dimitrov V.; Komatsu T.On the basis of the thermodynamical approach proposed by Takahashi and Yoshio the Ge-O single bond strengths BGe-O of GeO6 groups denoted as [GeO6], all bridging GeO4 groups denoted as [GeO 4]BO and GeO4 groups with one non-bridging oxygen denoted as [GeO4]-NBO have been determined for xNa 2O.(1-x)GeO2 (x = 5-30 mol%) glasses as follows: 323 kJ/mol for [GeO6], 341 kJ/mol for all bridging [GeO4]BO and 460 kJ/mol for [GeO4]-NBO groups. Equation for the calculation of average single bond strengths BM-O of sodium germanate glasses has been suggested taking into account the contribution of different structural units namely [GeO6], [GeO4]BO and [GeO 4]-NBO groups. It has been found that the average single bond strength BM-O of sodium germanate glasses decreases up to 267 kJ/mol at 25 mol% Na2O due to the formation of [GeO6] groups and increases up to 282.5 kJ/mol at 30 mol% Na2O due to the formation of [GeO4]-NBO groups. The results support the idea that the formation of [GeO6] groups is probably a main reason for the so-called germanate anomaly. The refractive index based optical basicity Λ(no) is sensitive in relation to the germanate anomaly effect and the group basicity follows the sequence: Λ[GeO4]BO < Λ[GeO6] < Λ[GeO4]-NBO. The observed correlation between Λ(no) and BM-O of sodium germanate glasses has been discussed with the presence of Ge(4)-O- Ge(4), Ge(4)-O-Ge(6) and Ge(4)-O-... Na(6) chemical bonds in the glass structure in which in bracket the coordination number of the cation is given. ©2009 The Ceramic Society of Japan.Item Correlation between thermal expansion coefficient and interionic interaction parameter in ZnOBi2O3B2O3 glasses(2018-01-01) Komatsu T.; Inoue T.; Tasheva T.; Honma T.; Dimitrov V.The volume thermal expansion coefficients (β) in 50300°C of xZnOyBi2O3zB2O3 glasses (x = 1065, y = 1050, z = 2560 mol%) were measured and the refractive index-based interionic interaction parameters A(no) were estimated from oxide ion electronic polarizabilities to acquire deeper insight into the relationship between the electronic polarizability and chemical bonding state of oxide glasses. The glasses have relatively large values of c = 210289.© 1017K11, and the substitution of ZnO for B2O3 and the increase in Bi2O3 content result in an increase in c. The values of A(no) decrease with the substitution of ZnO for B2O3 and the substitution of Bi2O3 for ZnO. An almost linear correlation was observed between c and A(no), i.e., the volume thermal expansion coefficient decreases with increases in the interionic interaction parameter. A good correlation was also observed between A(no) and the refractive index-based optical basicity a(no). The interionic interaction parameter is helpful for understanding the chemical bonding state of oxide glasses.Item Effect of interionic interaction on the electronic polarizability, optical basicity and binding energy of simple oxides(1999-01-01) Dimitrov V.; Komatsu T.Interaction parameter A proposed in Yamashita-Kurosawa's theory has been calculated for numerous single component oxides. It has been assumed that in the case of simple oxides it represents, through the electronic polarizabilities of the ionic pair the interaction between oxide ion and the corresponding cation due to overlapping of their outermost electronic orbitals to form a chemical bond. It has been proposed that the parameter A is closely related to the polarizability of the oxide ion as well as the optical basicity of the oxides. The obtained almost linear distribution of the basicity in respect to Yamashita-Kurosawa's parameter A could be used as an optical basicity scale for simple oxides. Systematic decrease of the O1s and outermost cation binding energies with decreasing interaction parameter has been established. It has been associated with decreased charge overlapping between electronic shells of the oxide ion and cation, which relates to large electronic polarizabilities of both cation and oxide ion and increased optical basicity, that is increased ionicity of the chemical bond.Item Electronic ion polarizability, optical basicity and metal (or nonmetal) binding energy of simple oxides(1999-01-01) Dimitrov V.; Komatsu T.A suitable relationship between free-ion polarizability and metal (or nonmetal) outermost binding energy has been searched on the basis of the similarity in physical nature between electron binding energy and ionization energy. It has been suggested that outermost core-level binding energy can be used for relative measuring the cation polarizability. In general, cation polarizability increases with decreasing metal (or nonmetal) binding energy. Highly polarizable cations possess low outermost binding energy. Simultaneously, a systematic periodic change of the polarizability against the binding energy has been observed in the isoelectronic series. A decreasing of metal (or nonmetal) binding energy in XPS spectra of simple oxides is accompanied with decreasing of O1s binding energy, that is related to increased basicity. This could be explained on the basis of enhanced interaction between outermost metal core level and O2p orbitals responsible to increased electron donor ability of oxide ion.Item Electronic polarizability, optical basicity and single bond strength of oxide glasses(2013-12-17) Dimitrov V.; Komatsu T.The current status of the development of the optical basicity concept and Sun's approach on single bond strength to Bi2O3-B2O3, ZnO-Bi2O3-B2O3 and R2O-B2O3-SiO2 (R = Li, Na and K) glasses has been discussed. In all glass systems the optical basicity increases with decreasing average single bond strength. More acidic glasses possess large BM-O (480-320kJ/mol) which means participation of an average oxide ion in more covalent M-BO (bridging oxygen) bonds such as B-O-B and Si-O-Si. The smallest values of BM-O about 300-250 kJ/mol have been obtained for bismithate glasses. It has been assumed that these values support the formation of Bi-O-B, Bi-O-Bi, Zn-O-B and Zn-O-Bi bonds with increased ionicity.Item Group optical basicity and single bond strength of lead borate glasses(2018-01-01) Dimitrov V.; Tasheva T.; Komatsu T.Equation providing the calculation of the theoretical optical basicity Λth(1) of PbO-B2O3 glasses is suggested taking into account the contribution of the mole fraction and the group basicity of different structural units, namely BO3 and BO4 groups. It is found that in case of PbO-B2O3 glasses the curves of the refractive index based optical basicity Λ(n0) and the theoretical optical basicity Λth(1) as a function of PbO content follow a similar trend changing their slope at about 50 mol. % PbO. An equation is proposed to calculate the average single bond strength BM-O of PbO containing borate glasses taking into account the mole fractions of PbO3, PbO4, PbO6, BO3 and BO4 groups. It is established that both equations give the possibility for more precisely estimation of the theoretical optical basicity and the single bond strength of the glasses. It is found that the single bond strength of PbO-B2O3 glasses decreases with increasing PbO content. The observed increase of the optical basicity with decreasing single bond strength of lead borate glasses is discussed with increase the number of Pb-O-B and Pb-O-Pb bonds containing oxide ions with increased polarizability.Item Group optical basicity and single bond strength of oxide glasses(2018-01-01) Dimitrov V.; Komatsu T.; Tasheva T.This paper is a review of our recent results in the field of group optical basicity of the oxide glasses. Dimitrov and Komatsu have recently introduced the concept of group (i.e. microscopic) optical basicity, proposed by Duffy and Ingram, to binary R2O (RO) - TeO2 (R = Na, Mg, Sr, Ba, Zn and Pb) and ternary 10R2O.10R'O.80TeO2 (R = Li, Na and K, R'= Mg, Ba and Zn) tellurite glasses based on N4 and N3 fractions of different Te4 and TeO3 groups. In fact, the group basicity of Te4 unit with one non-bridging oxygen (λTeO4 l - = 1.23), Te4 unit without non-bridging oxygen (λTeO4 l = 0.99) and a terminal TeO3 unit with two non-bridging oxygens (λTeO3 l - = 0.82) is evaluated. Equations for evaluation of the theoretical optical basicity Λth(1) of Na2O-B2O3, PbO-B2O3, Na2O-SiO2 and R2ORO- TeO2 glasses are advanced taking into account the contribution of the mole fraction and the group basicity of different structural units, namely BO3, BO4 and SiO4 groups. Equations providing the calculation of the average single bond strength BM-Oof Na2O-B2O3, PbO-B2O3B2O3, Na2OGeO 2, Bi2O3-B2O3 and ZnO-Bi2O3-B2O3 glasses are suggested considering the mole fractions of BO3, B4, Ge4, GeO6, PbO3, Pb4 and PbO6 groups. It is established that there is a general trend of optical basicity increase along with single bond strength decrease in borate-silicate-germanate-tellurite-bismuthate glasses sequence.Item Interionic interactions, electronic polarizability and optical basicity of oxide glasses(2000-01-01) Dimitrov V.; Komatsu T.Interaction parameter, A, proposed in Yamashita-Kurosawa's theory of dielectric constant, has been calculated for numerous binary oxide glasses on the basis of polarizability of oxide ion determined from refractive index. It has been established that the interaction parameter is closely related to the oxide ion polarizability and the optical basicity of the glasses. The almost linear distribution of the optical basicity obtained in the oxide glasses against the interaction parameter could be used as an optical basicity scale for the oxide glasses. It was established that the interionic interactions are strong in glasses formed by two acidic oxides and they become weaker in glasses formed by acidic and basic or two basic oxides. Generally, the interaction parameter decreases and optical basicity increases according to the sequence: phosphate, borate, silicate, germanate, tellurite, titanate glasses. It has been assumed on the basis of the known structural models and experimental results on the core level and valence band spectra of glasses that the interaction parameter represents the interionic interaction between cation and an averaged oxide ion due to overlapping of their outermost electronic orbitals to form a chemical bond. It was found that the decrease of interaction parameter correlates with small charge overlap and large cation and oxide ion polarizabilities, giving rise to an enhanced unshared oxide ion 2p electron density available for donation. The results obtained probably provide a good basis for prediction of interionic interaction in oxide glasses on the basis of refractive index.Item Polarizability, basicity and chemical bonding of single and multicomponent oxide glasses(2015-01-01) Dimitrov V.; Komatsu T.Refractive index based oxide ion polarizability, αO2-(no), and optical basicity, Λ(no), values are determined for B2O3, SiO2, P2O5, GeO2, TeO2, Ga2O3, As2O3, La2O3 and Sb2O3 single component glasses on the basis of their refractive index and density. Basicity values of 0.46 for B2O3 glass, 0.53 for SiO2 glass, 0.54 for P2O5 glass, 0.80 for GeO2 glass, 0.93 for Ga2O3 glass, 1.02 for As2O3 glass, 1.05 for TeO2 glass, 1.11 for Sb2O3 glass and 1.18 for La2O3 glass are advanced. They are slightly higher than those obtained for simple crystalline oxides. Chemical bonding parameters such as the refractive index based interaction parameter, A(no), and single bond strength BM-O are used to support the basicity data obtained. The correlation between the optical basicity, Λ(no), and single bond strength BM-O of some Sb2O3, Bi2O3 and TeO2 containing glasses is studied. It is found that in general a decrease in A(no) and BM-O is accompanied by Λ(no) increase. The applicability of thye observed correlations to nonlinear optics is also discussed.Item Polarizability, optical basicity and O1s binding energy of simple oxides(1999-01-01) Dimitrov V.; Komatsu T.; Sato R.A suitable relationship between oxide ion polarizability, cation polarizability, optical basicity and O1s binding energy in XPS spectra has been searched on the basis of experimental and calculated data reported in the literature for numerous simple oxides. It has been established that O1s binding energy decreases with increasing oxide ion polarizability, cation polarizability and optical basicity. The observed O1s chemical shift to lower binding energy from 533.5 eV to 528.2 eV could be explained with an increase in electron charge density of the oxide ions, due to an increase in their electronic polarizability. Increased oxide ion polarizability means stronger electron donor ability of the oxide ions and vice versa. That is why O1s binding energy can be used for the construction of common basicity scale of different amorphous and crystalline materials. On this basis the simple oxides have been separated into three groups according to the values of their oxide ion polarizability, optical basicity and O1s binding energy.