The magnetic properties of oxygen-hole aluminum centres in crystalline SiO₂. VI: A stable AlO₄/Li centre

Abstract

A new study, by electron paramagnetic resonance (EPR) spectroscopy at cryogenic temperatures, of aluminum oxygenic-hole centres in a α-quartz single crystal is reported. The well-known centre [AlO 4 ] 0 has been reinvestigated with somewhat improved techniques and computer analysis, confirming previous results in the literature. A previously unreported Al–Li centre has now been well characterized by EPR. From the fitted parameter matrices g, A( 27 Al), P( 27 Al), A( 7 Li), and P( 7 Li) we have determined not only that the hole resides on a "long-bonded" oxygen anion, as in [AlO 4 ] 0 , but have also established the position of the near-by interstitial lithium ion. One model for this centre is that it consists of a lithium atom Li 0 linked to the diamagnetic centre [AlO 4 ] – , yielding hole-bearing species [AlO 4 /Li] – via internal charge transfer. PACS Nos.: 7630Da, 7630Mi