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 [AlO4]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(27Al), P(27Al), A(7Li), and P(7Li) we have determined not only that the hole resides on a "long-bonded" oxygen anion, as in [AlO4]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 Li0 linked to the diamagnetic centre [AlO4]–, yielding hole-bearing species [AlO4/Li]– via internal charge transfer. PACS Nos.: 7630Da, 7630Mi