EXPERIMENTAL DISCRIMINATION BETWEEN BRIDGING AND NONBRIDGING OXYGEN - PHOSPHORUS BONDS IN P2O5, Na2O GLASS BY PULSED NEUTRON TOTAL SCATTERING

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1 EXPERIMENTAL DISCRIMINATION BETWEEN BRIDGING AND NONBRIDGING OXYGEN - PHOSPHORUS BONDS IN P2O5, Na2O GLASS BY PULSED NEUTRON TOTAL SCATTERING K. Suzuki, M. Ueno To cite this version: K. Suzuki, M. Ueno. EXPERIMENTAL DISCRIMINATION BETWEEN BRIDGING AND NON- BRIDGING OXYGEN - PHOSPHORUS BONDS IN P2O5, Na2O GLASS BY PULSED NEU- TRON TOTAL SCATTERING. Journal de Physique Colloques, 1985, 46 (C8), pp.c8-261-c < /jphyscol: >. <jpa > HAL Id: jpa Submitted on 1 Jan 1985 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2 JOURNAL DE PHYSIQUE Colloque C8, suppl6ment au n012, Tome 46, d6cembre 1985 page C8-261 EXPERIMENTAL DISCRIMINATION BETWEEN BRIDGING AND NONBRIDGING OXYGEN - PHOSPHORUS BONDS IN P205,Na20 GLASS BY PULSED NEUTRON TOTAL SCATTERING K. Suzuki and M. Ueno The Research Institute for Iron, SteeZ and Other Metals, Tohoku University, Katahira 2-1-1, Sendai 980, Japan RESLJ - Les liaisons oxygsne - phosphore pntantes et non-pntantes dans des verres p2 o5 - Na2 0 ont Bte differenciees 2 l'aide de la diffusion totale de neutrons pulses fournis par une source 2 spl1iation La loncpeur des liaisons pur les paires 0 - P non-pntantes est sensiblerent plus courte que pour les paires pntantes, aussi bien dans les verres que dans le cristal. Abstract - Bridging and nonbridging oxygen-phosphorus bond. existing in P2O5. Na20 glass have been distinguished by the pulsed neutron total scattering uslng a spallation neutron source. The bondlength for the nonbridging oxygen -phosphorus pair is significantly shorter than that for the bridging oxygenphosphorus pair in the glass as well as in the crystalline counterpart. The discrimination between the bridging and nonbridging oxygen atoms bound to a central glass-forming cation in the plyhedral structure units constructing the three ~sionalnetwork structure is one of the mst important keys for characterizing the short-range structure of oxide glasses. So far the measuranents of X-ray photoelectron spectros~~ have been carried out for identifying the bridging (0 ), nonbridging(0-) and free (0 ) oxygen atoms existing in silicate and phosphate glasses/l/. Misawa etal/z/have concluded from the high resolution measurement of the radial distribution function that Si-O- bondlength does significantly shrink compared with Si-OO bondlength in Na20-2Si02 glass as well as in Na2O.2SiO2 crystalline compound. mere is a significant difference of the bondlength between bridging oxygen-phosphorus bond (P-0 ) and nonbridging oxygen-phosphorus bond (P-O- or/and MO) in NaP03 crystalline cap3und/3,4/. Therefore it is interesting to examine whether such a difference of the bondlength is still preserved or not in the counterpart of NaP03 glass. In order to distinguish the P-OO and P-O-(or WO) bond on the radial distribution function in real space, we need to extend the measureroent of the structure factor SfQ) up to an enontwusly high value of the scattering vector Q(=4.rrsinO/X) such as beyond 30 to 40 A-I. The tim-of-flight pulsed neutron total scattering exprht based on accelerator neutron sources offers a quite pawerful technigue, because a relatively high flux of epitheml energy neutrons is easily supplied. This study aims at observing directly the separation of the bondlength and coordination nmkr between P-OO and P-Od(or WO) bond in P205-Na20 glass by the pulsed neutron total scattering. P205-Na20 glass was prepared by the same procedure done by Brady/5/. The glass sample was smashed into small pieces and then contained in a vanadium metal cylinder of nun in wall thickness, 7.8 nun in inner diameter and 70 mm in length. The measurement of S(Q) for the glass contained in the cylinder was made at room bnprature using a FO-F pulsed neutron total scattering spectrometer MARK I1 installed at the Tohoku University 300 E V electron LINAC/6/. During the rwasurement the glass sample con- Article published online by EDP Sciences and available at

3 JOURNAL DE PHYSIQUE Q(&') I I Fig. 1 - Neutron total structm factor S (Q) of P205 *Na20 glass. Fig. 2 - Radial. distribution functions(rdf) of P 0.Na 0 glass. The Fourier transform from S(Q) m is truncated at vxious vdds oz &.

4 JOURNAL DE PHYSIQUE C8-263 tained in the vanadium mtal cylinder cell was kept in a vacuum chamber to prevent it from hygroscapic reaction and also to eliminate the background due to air scattering of incident neutrons. The procedures of data processing and analysis have been fully described in a previous pap2r/7/. I11 - RESULTS AND DISCUSSION The exprirrental structure factor S (Q) of P205-Na20 glass rneasured up to Q= 40 is shown in Figure 1. The oscillatory behavior of the S(Q) is obviously found over the all range of Q examined in this study. Figure 2 shaws the radial distribution func- tion(fdf) which is defined as the Fourier transform of the S (Q) truncated at various values of &. Here the RDF mans 4?rr2pg(r). The first peak in the FDF is split into two s&paks, when & value is extended beyond 35 A-1. The first subpak is nearlylccatedat r=1.50 A, while the position of the second subpeak is r=1.64 A. It is not certain that these vdlues are final goals, because Figure 3 shows that the Qmax dependence of the split peak position is not saturated even at &= 40 A-l. If the short-range structure of P205.Na20 glass is assuroed to resemble that of the corresponding counterpart of NaP03 crystalline ampund such as listed in Table 1, the first and second subpeak can be surely assigned to the phosphorus-nonbridging oxygen (P-O-) bond and phosphorus-bridging oxygen (P-OO) bond existing in the glass res~ctively. Based on the least-squared fitting using the gaussian functions, as shown in Figure 4, it is concluded that the coordination nmkers of ncmbridging oxygen(0-) and Fig. 3 - & dependence of the position and area of the first peak in the RDF of P205.Na 0 glass. 2 Fig. 4 - The least-squared fitting using the gaussian functions is applied to the first peak profile of the RDF for P205-Na20 glass.

5 C8-264 JOURNAL DE PHYSIQUE Table 1 - Interatomic distances and coordination nmkers of 0 atoms bound to a P atom in P-O bonds existing in NaP03 and P205 crystalline compounds and P205-Na20 glass. Crystals Nonbridging Oxygen Bridging Oxygen P-0- or P=OO bond P-O0 bond Ref. rp-o (A) np+o (atoms) rpeo (A) np+o (atoms) Glass P205-Na This work Ar=0.05 (f0.1) Ar=0.05 (20.1) Ar is the fluctuation width of the bondlength obtained by the least-~ed fitting using the gaussian function. Bridging Fig. 5 - [PO4] structure unit in P205-Na20 glass.

6 bridging oxygen (Oo) atoms bound to a phosphorus atom are 2.1 and atoms in P205-Na20 glass. merefore the basic structure-unit constructing P205.Na20 glass is a distorted tetrahedron consisting of four 0 atoms, of which central hole is occupied by a P atan. 'It.lo 0- atoms are connected to the central P atom with the P-O- bondlength of 1.50 A, while two O0 atoms are bound to the central P atom with the P-OO bondlength of 1.64 A, as sham in Figure 5. Table 1 indicates that the both of P-O- and P-OO bondlength in the glass are longer than those in the crystalline ampun&. Hawever the P-OO bondlength is mre extended than the P-O- bondlength. Such a behavior has been observed in the case of silicate glasses, too/2/. A small peak located around r=3.0 A in the RDF corresponds to the P-P correlation in P205-Na2O glass. Tnerefore we can find that an average bondangle of wo-p is about 130 O in P205.Na20 glass. In contrast to silicate glasses, the Na+-O- correlation is not obviously distinguished f m the 0-0 correlation on the RDF of P205.Na20 glass. By subtracting the contribution of the 0-0 correlation from the second peak region, we can estimate that the coordination n d r of 0- atoms around a Na+ atom is approximately = 1.5~2.0 atoms. This is quite different from that " ~ ~ + 4 atoms % 5 has been often found in Si02-Na20 glass.?he authors would like to thank Prof. M-Misawa for his kind discussion, and the members of Nuclear Science Laboratory, Tohoku University for their operating the electron LINAC and developing the computer program of data aquisition. /1/ Anderson, R. P., "X-Ray Photmledron Spectrosaqy of Sodium Silicate Glass", Amr. Chem. Soc. Weting, New York, /2/Misawa, M., Price, D. L. and Suzuki, K., J. Non-Crystalline.Solids 37 (1980) 85. /3/McAdam, A., Jost, K. H. and Beagley, B., Acta Cryst., % (1968) 16x. /4/Jost, K. H., Acta Csyst., 16 (1963) 640. /5/Brady, G. W., J. Chem. ~hyz, 28 (1958) 48. /6/&no, M., Misawa, M. and ~uzukr; K., *s. Bp. Lab. Nucl. Sci., Tohoku University 13 (1980) 254. n/~uzuki, K., Misawa, M., Kai, K. and Watanabe, N., Nucl. Instrum. & ~thods 147 (1977) 519. ~Cruickshank, D. W. J., Acta Cryst., 2 (1964) 677 and 679.