Structure of Ternary Aluminum Metaphosphate Glasses

Abstract

Ternary metaphosphate glasses in the systems (1 – x)NaPO3·xAl(PO3)3, (1 – x)KPO3·xAl(PO3)3, and (1 – x)Pb(PO3)2·xAl(PO3)3 (0 ≤ x ≤ 1) were analyzed using a set of 31P, 27Al, and 23Na high-resolution NMR and X-ray photoelectron spectroscopy techniques, to determine the phosphate speciation and the short- and medium-range order properties of the P and Al connectivity. O-1s XPS data confirm that the number of oxygen atoms linking two phosphorus remains close to 33% for all of the glasses, consistent with the exclusive presence of Q2 units, in agreement with 31P MAS NMR data. The increasing formation of Al–O–P linkages with increasing x is indicated by a new O-1s peak, with binding energies near 532 eV, and systematic changes in the 31P MAS NMR chemical shifts. The presence of Q2 m phosphate groups (m being the number of P–O–Al bonds per tetrahedron, 0 ≤ m ≤ 2) was analyzed by 31P MAS NMR and 31P{27Al} REAPDOR experiments. The REDOR technique was applied to the heteronuclear spin systems 31P/27Al and 31P/23Na, to analyze the local structure around these species. 27Al MAS NMR and 27Al triple quantum MAS were applied respectively to determine the coordination state of Al and the values of isotropic chemical shift and electric quadrupole coupling parameters of 27Al. The results points to common features in the glass structure of these ternary phosphates. The most probable environment of Al has six close P atoms, with no evidence of Al–O–Al bonds, showing that the connection between AlO n and PO4 is attained through corners. There is no evidence of local segregation of cationic species in the phosphate matrix. A definite precedence in the formation of Q2 m units was found as the Al concentration is increased, consisting of the progressive conversion of Q2 0 to Q2 1 and then Q2 1 to Q2 2 units with increasing x. Up to intermediate values of x, the speciation shows an above-random trend compatible with a binary distribution {Q2 0,Q2 1} for the K–Al and Pb–Al systems.

An Assessment of the Effect of Relative Humidity on the Decomposition of the ZDDP Antiwear Additive

“…6 indicate that as iron replaces zinc, the phosphate chain length decreases significantly. Similarly, numerous previous studies [38,39,41,42] showed that the presence of metallic cations, e.g. FeO or ZnO, in phosphate glasses reduces the phosphate chains length.…”

Tunable luminescence from bismuth‐doped phosphate laser glass by engineering photonic glass structure

“…Figure A illustrates the 27 Al MAS NMR spectra of samples P– x Al–5Zn–1Bi. There are three peaks at ~36 ppm, ~7 ppm, and ~‐16 ppm, which correspond to tetrahedral (AlO 4 ), hexahedral (AlO 5 ), and octahedral (AlO 6 ), respectively. Aluminum octahedra are the dominant species over the other.…”

“…At the same time, the polymerization of the PO 4 chains change accordingly. Usually, chemical shifts at −13, −30, −45 ppm correspond to the Q 1 , Q 2 , and Q 3 groups of PO 4 tetrahedra where the exponent in Q n denotes the number of bridging oxygen around phosphorus . The peak shift from −31.8 ppm to −34.6 ppm implies the increase in Q 3 species of PO 4 tetrahedra within the glass network (see Figure ).…”

“…Once aluminum ions are introduced, they will exist in forms of tetrahedral (AlO 4 ), hexahedral (AlO 5 ) and octahedral (AlO 6 ). Octahedral aluminum ions will play as glass modifiers, hexahedral aluminum will be as intermediate while tetrahedral aluminum will be glass formers . As the bigger cations of tetrahedral aluminum (R = 0.53 Å) substitute for smaller phosphorus ions (R = 0.31 Å), the local glass network will expand.…”

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“…Al MQMAS spectrum of the sample with x = 30 and Table 5 summarizes the results obtained for all the samples. 24,26,74 In Figure 18 the results for a fluoride free glass and a glass having the maximum F content are compared. The dipolar second moments (M 2 ) were obtained from the parabolic fitting in Equation 47 and the results are summarized in Table 6.…”