Abstract

Metastable electron-hole centers in single crystals of Amelia albite were studied using electron paramagnetic resonance at 9.2 GHz between 5 and 260 K. Six distinct O1- centers were identified as four O1-/227Al centers, one O1-/27Al × 223Na center, and one O1-/[Si,M2+] center. Values of their g and A tensors and limits of thermal stabilities were determined.

The four O1-/227 Al centers could be assigned to AlT1(0)-OC(O)-AlT2(m), AlD(O)-AlT2(m), AlT2(0)-OC(m)-AlT1(m), and AlT2(0)-OD(m)-AlT1(m) bridges (violations of the rule of Loewenstein) and are designated as co, do, cm, and dm, respectively. Their total concentration was estimated to be 2 × 10-4 to 3 × 10-4 per formula unit NaAlSi3O8. Their spectra could be observed between 5 and 220 K, the maximum intensities being near Tm = 60 K. They were destroyed after heating at 523 K for 3 h. The calculated density of the O1- (2p5) unpaired electron at the tetrahedral A1 position is about 0.006 e.

The O1-/27 A1 × 223Na center could be assigned to a SiT1(0)-OA1,-AlT1(m) bridge and is designated as a’1. Its estimated concentration is at least 1 × 10-4 per formula unit. The spectrum could be observed between 20 and 120 K, Tm ≈ 110 K. It was destroyed after heating at 493 K for 3 h. The O1- (2p5) unpaired electron density at the A1 position is about the same as that of the O1-/227A1 center and 0.002 e at the two adjacent Na positions. The covalent participation in the Al-O bond is at least 50% greater than that of A1 sub-stituted for Si in quartz.

The O1-/[Si,M2+] center could be assigned to O1- at the D(m) position that links T2(0) with T1(m) and is designated as hm. Its estimated concentration is at least 1 × 10-4 per formula unit. Its line could be observed between 10 and 260 K, Tm ≈ 115 K. It was destroyed after heating at 623 K for 3 h.

After destruction by heating, all centers could be reactivated by X-rays.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.