[Paper Review] Luminescence of alpha-quartz

A.N. Trukhin, Kaspars Truhins|arXiv (Cornell University)|Sep 19, 2012

Glass properties and applications6 references5 citations

TL;DR

This review synthesizes 30 years of research on luminescence in alpha-quartz, focusing on self-trapped excitons (STE) emitting at 2.6–2.7 eV under ionizing radiation with ~0.2 quantum yield, and defect-related luminescence induced by irradiation. Key findings include distinct luminescence bands from AlO4–Me complexes (6 eV at low T, 3.4 eV), Ge-related STE, and noble metal dopants (Cu at 3.4 eV, Ag at 4.75 eV), all reversible upon ion exchange.

ABSTRACT

Among the host materials luminescence the luminescence of the self-trapped exciton (STE) is reviewed. This luminescence, which band is situated at 2.6 to 2.7 eV, could be observed mainly under ionising radiation with energetic yield about 0.2. The STE does not participate in pure recombination processes. Host material defect luminescence at 5 eV appears in alpha-quartz after heavy irradiation. It is constituted of permanent defect after neutron irradiation and transient defect after dens electron beam irradiation. This luminescence could be observed well at temperatures below 60 K. All another luminescence are of impurity nature. The Ge impurity luminescence in alpha-quartz explained as STE near Ge. The aluminium and alkali complexes. One of them is with UV band at 6 eV, appears at low temperatures and could be excited only in tunnelling recombination process between pairs (AlO4 Me), where Me is an alkali ion captured an electron and a hole remains on aluminium tetrahedron. Another luminescence with band at 3.4 eV is also luminescence of complexes (AlO4 Me), which behaviour is similar to the luminescence of alkali alumosilicate glass. The third luminescence with band at 3 eV could be observed mainly in natural alpha-quartz, bright at temperatures below 200 K and is interpreted as STE like luminescence at alumosilicate clasters. The exchange of alkali ions to noble ions of copper of silver reduces original luminescence of alumo alkali complexes and luminescence of noble ions appears. The main band of copper related luminescence is at 3.4 eV and that of silver is at 4.75 eV, both could be observed up to 500 K. their nature could be well described in terms of intraions transition. Exchange of noble ions back to alkali ions renews initial luminescence of the samples.

Motivation & Objective

• To systematically review the luminescence properties of alpha-quartz over three decades of research.
• To identify and characterize the origins of various luminescence bands, including self-trapped excitons and defect-related emissions.
• To clarify the role of impurities (Ge, Al, alkali, Cu, Ag) in shaping luminescence behavior under different irradiation and temperature conditions.
• To explain the reversible nature of luminescence changes upon alkali-to-noble ion exchange and back.

Proposed method

• Analysis of experimental data from decades of luminescence spectroscopy on natural and irradiated alpha-quartz samples.
• Use of temperature-dependent luminescence measurements to distinguish between transient and permanent defects.
• Application of tunneling recombination models to explain excitation mechanisms in AlO4–Me complexes.
• Comparison of luminescence behavior in synthetic and natural quartz to identify intrinsic vs. impurity-related emissions.
• Ion exchange experiments to study the reversibility of luminescence changes upon substitution of alkali ions with Cu or Ag.
• Correlation of emission bands with specific defect structures (e.g., (AlO4Me), Ge-related centers, noble ion states).

Experimental results

Research questions

• RQ1 What causes the 2.6–2.7 eV luminescence band in alpha-quartz, and why is it associated with self-trapped excitons?
• RQ2 How do neutron and electron beam irradiation differentially affect defect-related luminescence in alpha-quartz?
• RQ3 What is the origin of the 6 eV luminescence band observed at low temperatures in AlO4–Me complexes?
• RQ4 How do Cu and Ag dopants alter the luminescence of alumo-alkali complexes in alpha-quartz?
• RQ5 To what extent is the luminescence behavior of doped alpha-quartz reversible upon ion exchange?

Key findings

• The self-trapped exciton (STE) luminescence in alpha-quartz emits at 2.6–2.7 eV and has a quantum yield of approximately 0.2 under ionizing radiation.
• A 5 eV defect luminescence band appears after heavy irradiation, originating from permanent defects after neutron irradiation and transient defects after electron beam irradiation, observable below 60 K.
• The 6 eV luminescence band in AlO4–Me complexes arises from tunneling recombination processes and is only observable at low temperatures.
• A 3.4 eV luminescence band from AlO4–Me complexes is similar to that in alkali aluminosilicate glass and is prominent below 200 K.
• Copper doping introduces a main luminescence band at 3.4 eV, while silver doping produces a band at 4.75 eV, both stable up to 500 K and attributed to intra-ionic transitions.
• Ion exchange between alkali and noble ions (Cu, Ag) reversibly alters luminescence: replacing alkali with Cu or Ag quenches original complex luminescence, and reverting the ions restores the initial emission.