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Local Structure of Amorphous (PbO)<INF>x</INF><INF></INF>[(B<INF>2</INF>O<INF>3</INF>)<INF>1</INF><INF>-</INF><INF>z</INF><INF></INF>(Al<INF>2</INF>O<INF>3</INF>)<INF>z</INF><INF></INF>]<INF>y</INF><INF></INF>(SiO<INF>2</INF>)<INF>y</INF><INF></INF> Dielectric Materials by Multinuclear Solid State NMR

Authors :
Sawvel, A. M.
Chinn, S. C.
Bourcier, W. L.
Maxwell, R. S.
Source :
Chemistry of Materials; March 2005, Vol. 17 Issue: 6 p1493-1500, 8p
Publication Year :
2005

Abstract

Structural speciation of glasses in the systems PbO−B&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;−SiO&lt;INF&gt;2&lt;/INF&gt;, PbO−B&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;−Al&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;−SiO&lt;INF&gt;2&lt;/INF&gt;, and PbO−Al&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;−SiO&lt;INF&gt;2&lt;/INF&gt; were studied using solid state &lt;SUP&gt;29&lt;/SUP&gt;Si, &lt;SUP&gt;27&lt;/SUP&gt;Al, &lt;SUP&gt;11&lt;/SUP&gt;B, and &lt;SUP&gt;207&lt;/SUP&gt;Pb nuclear magnetic resonance (NMR) and Raman spectroscopy. Application of these methods provided insight into the role of Al&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt; incorporation in the lead borosilicate glass networks. The general composition range studied was (PbO)&lt;INF&gt;x&lt;/INF&gt;[(B&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;)&lt;INF&gt;1&lt;/INF&gt;&lt;INF&gt;-&lt;/INF&gt;&lt;INF&gt;z&lt;/INF&gt;&lt;INF&gt;&lt;/INF&gt;(Al&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;)&lt;INF&gt;z&lt;/INF&gt;&lt;INF&gt;&lt;/INF&gt;]&lt;INF&gt;y&lt;/INF&gt;&lt;INF&gt;&lt;/INF&gt;(SiO&lt;INF&gt;2&lt;/INF&gt;)&lt;INF&gt;y&lt;/INF&gt;&lt;INF&gt;&lt;/INF&gt; where x = 0.35, 0.5, and 0.65, y = (1 − x)/2 and z = 0.0, 0.5, and 1.0. Additional insight was obtained via &lt;SUP&gt;27&lt;/SUP&gt;Al 2D-3QMAS experiments. The &lt;SUP&gt;207&lt;/SUP&gt;Pb spin−echo mapping spectra showed a transition from ionic (Pb&lt;SUP&gt;2+&lt;/SUP&gt;) to covalently bound lead species with increased PbO contents in the borosilicate glasses. The addition of aluminum to the glass network further enhanced the lead species transition, resulting in a higher relative amount of covalent lead bonding in the high PbO content alumino-borosilicate glass. The number of BO&lt;INF&gt;4&lt;/INF&gt; units present in the &lt;SUP&gt;11&lt;/SUP&gt;B MAS NMR decreased with increasing PbO contents for both the borosilicate and the alumino-borosilicate glass systems, with the addition of aluminum further promoting the BO&lt;INF&gt;3&lt;/INF&gt; species. A deshielding of the &lt;SUP&gt;11&lt;/SUP&gt;B chemical shifts and the &lt;SUP&gt;27&lt;/SUP&gt;Al chemical shifts with increased lead contents (independent of changes in the quadrupolar coupling) was also observed for both glass systems and was attributed to an increasingly homogeneous glass structure. The &lt;SUP&gt;29&lt;/SUP&gt;Si spectra of the borosilicate and alumino-borosilicate glasses showed a downfield shift with increased PbO concentrations representing incorporation of Pb into the silicate and aluminosilicate networks. The Raman spectra were characterized by increased intensities of Si−O−Pb peaks and decreased intensities of Q&lt;SUP&gt;3&lt;/SUP&gt; peaks with increased PbO contents and showed no evidence of BO&lt;INF&gt;3&lt;/INF&gt; or BO&lt;INF&gt;4&lt;/INF&gt; ring species. Both the NMR and the Raman data point toward systems where lead is increasingly incorporated into the B&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;−SiO&lt;INF&gt;2&lt;/INF&gt; and the B&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt;−SiO&lt;INF&gt;2&lt;/INF&gt;−Al&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt; networks at high PbO concentrations, with the addition of Al&lt;INF&gt;2&lt;/INF&gt;O&lt;INF&gt;3&lt;/INF&gt; enhancing the trend.

Details

Language :
English
ISSN :
08974756
Volume :
17
Issue :
6
Database :
Supplemental Index
Journal :
Chemistry of Materials
Publication Type :
Periodical
Accession number :
ejs7310030

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