Detection of defects in minerals by luminescence spectroscopy

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1 Detection of defects in minerals by luminescence spectroscopy Jens Götze TU Bergakademie Freiberg Sm 3+ rel. intensity [counts] Eu 2+ Dy 3+ Sm 3+ Nd

2 Content 1. Physical basics of luminescence phenomena 2. Defects in minerals and the luminescence signal 3. Factors influencing the luminescence properties of minerals - typomorphic properties (quartz) - crystal chemistry (feldspar minerals) - aspects of quantitative luminescence spectroscopy 4. Conclusions

3 Physical basics of luminescence phenomena???

4 asics of luminescence Luminescence = transformation of diverse kinds of energy into visible light Luminescence of inorganic and organic substances results from an emission transition of anions, molecules or a crystal from an excited electronic state to a ground state with lesser energy. (Marfunin1979)

5 asics of luminescence Main processes of luminescence (1) absorption of excitation energy and stimulation of the system into an excited state (2) transformation and transfer of the excitation energy (3) emission of light and relaxation of the system into an unexcited condition

6 asics of luminescence Excitation by energy UV thermal excitation electrons biological processes photoluminescence thermoluminescence cathodoluminescence bioluminescence e - Schematic model of luminescence processes Emission of light

7 asics of luminescence The band model

8 asics of luminescence Energy levels in a band scheme for different crystal types E conduction band band gap band gap E (photo energ valence band conductor semiconductor insulator insulator

9 asics of luminescence radiationless transition (a) (b) (c) (d) E 1 2 Conduction band trap luminescence activator Valence band intrinsic luminescence extrinsic luminescence

10 asics of luminescence The configurational coordinate model

11 asics of luminescence excited state absorption band ground state emission band Configurational coordinate diagram for transitions according to the Franck-Condon principle with related absorption and emission bands, respectively. (modified after Yacobi & Holt 1990)

12 asics of luminescence Stokes shift 2 1 Excitation (1) and emission (2) spectra of Mn 2+ in calcite (after Medlin 1964)

13 Defects in minerals and the luminescence signal???

14 efects in minerals and the luminescence signal Importance of spatially resolved analyses! Detection of the real structure (defect structure) (1) Luminescence microscopy contrasting of different phases visualization of defects, zoning and internal structures of solids (2) Luminescence spectroscopy determination of the real structure detection of defects, trace elements their valence and structural position apatite o cc rel. intensity [counts] Eu 2+ Dy 3+ Sm 3+ Sm 3+ Nd wavelength [nm]

15 efects in minerals and the luminescence signal Luminescence centres intrinsic extrinsic pure lattice defects (broken bonds, vacancie trace elements (Mn 2+, REE 2+/3+, etc.) transition metal ions (e.g., Mn 2+, Cr 3+, Fe 3+ ) rare earth elements (REE 2+/3+ ) actinides (especially uranyl UO 2+ 2 ) heavy metals (e.g., Pb 2+, Tl + ) electron-hole centres (e.g., S 2-, O 2-, F-centres) crystallophosphores of the ZnS type (semiconductor) more extended defects (dislocations, clusters, etc.)

16 efects in minerals and the luminescence signal The crystal field theory (Burns, 1993) local environment of the activator ion Factors of the crystal field influence (crystal field splitting or 10Dq): ligands activator - type of the activator ion (size, charge, electron configuration) - type of the ligands - the interaction distance - local symmetry of the ligand environment, etc. the stronger the interaction of the activator ion with the lattice, the greater are the Stokes shift and the width of the emission line

17 efects in minerals and the luminescence signal rel. intensity [counts] Influence of the crystal field on luminescence emission spectra (1) influence of the crystal field = weak zircon Dy 3+ zircon scheelite Dy 3+ Dy 3+ Sm 3+ Sm 3+ Dy Dy 3+ Dy Dy wavelength [nm] anhydrite calcite fluorite apatite Sm 3+ Tm 3+ Sm 3+ Tb [nm] CL spectra of narrow emission lines (e.g. REE 3+ ) CL emission spectra are specific of the activator ion

18 efects in minerals and the luminescence signal Influence of the crystal field on luminescence emission spectra (2) influence of the crystal field = strong 400 rel. intensity [counts] calcite Mn 2+ Mn 2+ activated CL of CaCO 3 : aragonite green (~560 nm) calcite yellow-orange (~610 nm) magnesite red (~655 nm) wavelength [nm] CL spectra of broad emission bands (e.g. Mn 2+, Fe 3+ ) CL emission spectra are specific of the host crystal

19 efects in minerals and the luminescence signal Influence of the crystal field on luminescence emission spectra rel. intensity [counts] plagioclase Mn 2+ red Fe 3+ IR wavelength [nm] lunar plagioclases wavelength [nm] An content [mol-%] Position of the Fe 3+ activated CL emission band in plagioclases in relation to the anorthite content

20 Factors influencing the luminescence properties of minerals

21 Mineral groups and minerals showing CL in general all insulators and semiconductors elements sulfides oxides halides sulfates phosphates carbonates silicates diamond sphalerite corundum, cassiterite, periclase fluorite, halite anhydrite, alunite apatite calcite, aragonite, dolomite, magnesite feldspar, quartz, zircon, kaolinite technical products (synthetic minerals, ceramics, glasses!)

22 actors influencing the luminescence properties of minerals 1. Typomorphic properties Minerals show characteristic luminescence properties in dependence on their specific conditions of formation.

23 Quartz (SiO 2 ) close relationship between specific conditions of quartz formation, real structure and luminescence properties of quartz may provide important genetic information

defects in the crystal structure dislocations (two-dimensional)

24 SiO 4 -tetrahedra O Real structure of quartz one-dimensional point defects (1) defects of trace elements (2) pure lattice defects O Si O O defects in the crystal structure dislocations (two-dimensional) three-dimensional fluid and mineral inclusions fingerprints of the formation history

25 Real structure of quartz Detection of defects by Electron Spin Resonance (ESR) Luminescence Spectroscopy

26 Paramagnetic defects in quartz (Plötze 1995)

27 Characteristic CL emission bands in quartz (modified after Götze et al. 2001) Emission Suggested activator References 175 nm (7.3 ev) intrinsic emission of pure SiO 2 Entzian & Ahlgrimm (1983) 290 nm (4.28 ev) oxygen vacancy Jones & Embree (1976) nm oxygen vacancy Rink et al (1993) ( ev) [AlO 4 /Li + ] centre Demars et al. (1996) [TiO 4 /Li + ] centre Plötze & Wolf (1996) nm [AlO 4 /M + ] centre; M + = Li +, Na +, H + Alonso et al. (1983) ( ev) [H 3 O 4 ] 0 hole centre Young & McKeever (1990) 450 nm (2.8 ev) self-trapped exciton (STE) Stevens Kalceff & Phillips (1995) nm extrinsic emission Itoh et al. (1988) ( nm) [AlO 4 /M + ] 0, GeO 4 /M + ] 0 centres McKeever (1984), Götze et al. (2004) 580 nm (2.1 ev) E centre (oxygen vacancy) Rink et al. (1993); Götze et al. 1999) nm nonbridging oxygen hole centre (NBOHC) Siegel & Marrone (1981) ( ev) with several precursors Stevens Kalceff & Phillips (1995) 705 nm (1.7 ev) substitutional Fe 3+ Pott & McNicol (1971)

450 nm and 650 nm CL emission bands 2500 2 1 rel.

400 µm 0 300 400 500 600 700 800 wavelength [nm] Quartz from

28 450 nm and 650 nm CL emission bands rel. intensity [counts] µm Rochlitz 400 µm wavelength [nm] Quartz from rhyolite, Thunder Bay (Canada) most common CL emissions in igneous quartz

intensity [counts] 1300 1200 1100 1000 orange rim

29 Radiation halos in quartz grains of the U/Au deposit Witwatersrand, RSA 1400 Witwatersrand rel. intensity [counts] orange rim violet 300 µm blue core wavelength [nm]

30 Characteristic CL emission bands in quartz (modified after Götze et al. 2001) Emission Suggested activator References 175 nm (7.3 ev) intrinsic emission of pure SiO 2 Entzian & Ahlgrimm (1983) 290 nm (4.28 ev) oxygen vacancy Jones & Embree (1976) nm oxygen vacancy Rink et al (1993) ( ev) [AlO 4 /Li + ] centre Demars et al. (1996) [TiO 4 /Li + ] centre Plötze & Wolf (1996) nm [AlO 4 /M + ] centre; M + = Li +, Na +, H + Alonso et al. (1983) ( ev) [H 3 O 4 ] 0 hole centre Young & McKeever (1990) 450 nm (2.8 ev) self-trapped exciton (STE) Stevens Kalceff & Phillips (1995) nm extrinsic emission Itoh et al. (1988) ( nm) [AlO 4 /M + ] 0, GeO 4 /M + ] 0 centres McKeever (1984), Götze et al. (2004) 580 nm (2.1 ev) E centre (oxygen vacancy) Rink et al. (1993); Götze et al. 1999) nm nonbridging oxygen hole centre (NBOHC) Siegel & Marrone (1981) ( ev) with several precursors Stevens Kalceff & Phillips (1995) 705 nm (1.7 ev) substitutional Fe 3+ Pott & McNicol (1971)

31 500 nm CL emission band (transient CL) rel. intensity [counts] initial final initial quartz of pegmatite Brattekleiv, Norway after 100 s 400 µm wavelength [nm] Quartz from pegmatite, Brattekleiv (Norway) most common CL emission in pegmatitic quartz (hydrothermal quartz)

32 Characteristic CL emission bands in quartz (modified after Götze et al. 2001) Emission Suggested activator References 175 nm (7.3 ev) intrinsic emission of pure SiO 2 Entzian & Ahlgrimm (1983) 290 nm (4.28 ev) oxygen vacancy Jones & Embree (1976) nm oxygen vacancy Rink et al (1993) ( ev) [AlO 4 /Li + ] centre Demars et al. (1996) [TiO 4 /Li + ] centre Plötze & Wolf (1996) nm [AlO 4 /M + ] centre; M + = Li +, Na +, H + Alonso et al. (1983) ( ev) [H 3 O 4 ] 0 hole centre Young & McKeever (1990) 450 nm (2.8 ev) self-trapped exciton (STE) Stevens Kalceff & Phillips (1995) nm extrinsic emission Itoh et al. (1988) ( nm) [AlO 4 /M + ] 0, GeO 4 /M + ] 0 centres McKeever (1984), Götze et al. (2004) 580 nm (2.1 ev) E centre (oxygen vacancy) Rink et al. (1993); Götze et al. 1999) nm nonbridging oxygen hole centre (NBOHC) Siegel & Marrone (1981) ( ev) with several precursors Stevens Kalceff & Phillips (1995) 705 nm (1.7 ev) substitutional Fe 3+ Pott & McNicol (1971)

390 nm CL emission band (transient CL) initial 12000 after 60s rel.

700 800 wavelength [nm] Initial cathodoluminescence signal and spectral emission after

33 390 nm CL emission band (transient CL) initial after 60s rel. intensity [counts] initial after final 60s wavelength [nm] Initial cathodoluminescence signal and spectral emission after 60 s of electron irradiation 300 µm most common CL emission in hydrothermal quartz (also synthetic quartz!)

34 Characteristic CL emission bands in quartz (modified after Götze et al. 2001) Emission Suggested activator References 175 nm (7.3 ev) intrinsic emission of pure SiO 2 Entzian & Ahlgrimm (1983) 290 nm (4.28 ev) oxygen vacancy Jones & Embree (1976) nm oxygen vacancy Rink et al (1993) ( ev) [AlO 4 /Li + ] centre Demars et al. (1996) [TiO 4 /Li + ] centre Plötze & Wolf (1996) nm [AlO 4 /M + ] centre; M + = Li +, Na +, H + Alonso et al. (1983) ( ev) [H 3 O 4 ] 0 hole centre Young & McKeever (1990) 450 nm (2.8 ev) self-trapped exciton (STE) Stevens Kalceff & Phillips (1995) nm extrinsic emission Itoh et al. (1988) ( nm) [AlO 4 /M + ] 0, GeO 4 /M + ] 0 centres McKeever (1984), Götze et al. (2004) 580 nm (2.1 ev) E centre (oxygen vacancy) Rink et al. (1993); Götze et al. 1999) nm nonbridging oxygen hole centre (NBOHC) Siegel & Marrone (1981) ( ev) with several precursors Stevens Kalceff & Phillips (1995) 705 nm (1.7 ev) substitutional Fe 3+ Pott & McNicol (1971)

intensity [counts] 1000 950 900 850 300 400 500 600 700

35 580 nm CL emission band Hydrothermal quartz, Neves Corvo (Portugal) 1050 Agate from Chemitz (Germany) rel. intensity [counts] wavelength [nm] 400 µm most common CL emission in hydrothermal quartz

rel. intensity [counts] 40000 transient blue CL 30000 20000 10000 0 300 400 500 600 700 800

wood remains from Chemnitz, Germany wavelength [nm] Pol 25000 secondary rel.

36 rel. intensity [counts] transient blue CL Primary (yellow CL) and secondary (transient blue CL) silicification in petrified wood remains from Chemnitz, Germany wavelength [nm] Pol secondary rel. intensity [counts] yellow CL wavelength [nm] primary Dadoxylon sp.

37 Use of quartz CL colours for evaluating the provenance of clastic sediments single source mixed source ign ign met vol 200 µm 200 µm

38 Quartz is one of the purest minerals (used as a standard material) but it may show very different luminescence behaviour!

39 actors influencing the luminescence properties of minerals 2. Crystal chemistry K Al Al Na Li Fe Ge Ti Incorporation of activator elements and luminescence behaviour depend on: 1. crystallographic factors 2. specific physico-chemical conditions of crystallisation

Ehrenfriedersdorf granite Svensken alkaline rock rel.

intensity [counts] 2800 2400 2000 1600 1200 Eu 2+ Dy 3+ Dy 3+

wavelength [nm] 800 300 400 500 600 700 800 900 1000

40 Ehrenfriedersdorf granite Svensken alkaline rock rel. intensity [counts] initial final Mn 2+ rel. intensity [counts] Eu 2+ Dy 3+ Dy 3+ Sm 3+ Sm 3+ Sm 3+ Nd3+ 3+ Sm wavelength [nm] wavelength [nm] Luminescence behaviour of apatite from different geological environments

41 Feldspar minerals MT 4 O 8 alumosilicates T site: SiO 4 /AlO 4 tetrahedra K-Na-Ca series K[AlSi 3 O 8 ] sanidine orthoklase microcline alkali feldspar a[alsi 3 O 8 ] lbite plagioclase Ca[Al 2 Si 2 O 8 ] anorthite M site: cations (K,Na,Ca,Ba) Substitution: T site: Fe, Ti, Ga, B, Ge, P, Be, Sn, AlSiP M site: Sr, Ba, Li, Rb, Mn, Cu, Pb, Tl, REE, NH

42 Defect centres in feldspar minerals (after Petrov 1994) Thermal stable centres plagioclase cations Fe 3+ and Mn 2+ with d 5 electron configuration redox conditions Thermal matastable centres (reactivation by natural or artificial irradiation) microcline (amazonite) cations with uncommon valence (Ti 3+, [Pb-Pb] 3+ ) anions with uncommon valence (several types of O - defects) BO mn radicals (SiO 3-3, SiO 3-3 /Al, PO 2-3, NO 2 ) organic radicals (C 2 H 5, CH 3 ) Most frequent centres responsible for CL in natural feldspars: O - defects and Mn 2+, Fe 3+

43 Luminescence emissions and associated activators in feldspars Activator colour Peak Method Reference IR visible UV Tl + UV 280 nm PL Gorobets et al. (1989) Pb 2+ UV 280 nm TL Tarasshchan et al. (1975) Ce 3+ UV 355 nm CL Laud et al. (1971) Eu 2+ blue 420 nm CL,TL,RL Mariano & Ring (1975), Jaek et al. (1996) Cu 2+ blue 420 nm CL,TL,RL Mariano & Ring (1975), Jaek et al. (1996) Al-O - -Al blue nm CL,TL,RL Marfunin (1979), Walker (1985) O - -Si...M + bluish-green nm TL,RL Marfunin & Bershov (1970) Mn 2+ yellow nm CL,TL Sippel & Spencer (1970) Fe 3+ red/ir nm CL,TL,RL Sippel & Spencer (1970), Götze et al. (2000) REE 3+ UV-vis-IR several peaks CL Mariano et al. (1973), Götze et al. (2000) Pb +? IR ~860 nm CL, RL Trautmann et al. (1999), Erfurt (2003)

44 CL of feldspar mainly activated by electron defects rel. intensity [counts] Al-O - -Al Si-O -...M 2+ orthoclase Bodenmais Fe 3+ Orthoclase Bodenmais (Germany) wavelength [nm]

45 Fe 3+ activated CL in feldspar rel. intensity [counts] Fe 3+ o wavelength [nm] lbite (Khaldzan Buregte, Mongolia)

46 Shift of the Fe 3+ emission in alkali feldspars and plagioclases in dependence on the chemical composition peak-wavelength in nm alkali feldspar terrestrial plagioclases lunar plagioclases peak-wavelength in nm An content in mol-% Or content in mol-%

47 Mn 2+ activated CL in feldspar rel. intensity [counts] Mn wavelength [nm] celsiane, Big Creek

4000 1 Changes in Mn 2+ and Fe 3+ incorporation into feldspar due to varying physico-chemical conditions of crystallisation rel.

48 Changes in Mn 2+ and Fe 3+ incorporation into feldspar due to varying physico-chemical conditions of crystallisation rel. intensity [counts] Mn 2+ Fe wavelength [nm] anorthite, Monzoni 1 2 o o rel. intensity [counts] Fe µm wavelength [nm]

Dy activated luminescence) 3+ 1200 950 1000 900 green CL violet CL 800 850 300 400 500 600 700 800 900

49 rel. intensity [counts] Mn Detection of alteration processes in feldspar (REE Dy activated luminescence) green CL violet CL rel. intensity [counts] 1100 Dy 3+ Sm 3+ Sm 3+ Nd 3+ wavelength [nm] wavelength [nm] 8.3 ppm Mn 1.3 ppm M Pol 1 o o µm albite, Spruce Pine (USA)

50 actors influencing the luminescence properties of minerals 3. Aspects of quantitative luminescence spectroscopy

51 Factors influencing the luminescence properties/intensity!!!??? analytical factors type of equipment crystalllographic factors luminescence activation analytical conditions (excitation, temperature, etc.) sample preparation sensitizing quenching (e.g. quencher elements - Fe, concentration quenching) time (especially transient luminescence)

52 Luminescence activation rel. intensity [counts] Mn wavelength [nm] Mn 2+ activated CL in calcite o o o 300 µm

53 Luminescence activation (Götte & Richter 2004) Correlation of results of quantitative CL with PIXE for the Mn content in carbonates

54 Luminescence activation rel. intensity [counts] Al-O - -Al Mn wavelength [nm] zone 1-7 ppm Mn zone 2-31 ppm Mn zone 3-23 ppm Mn zone 4-14 ppm Mn Fe 3+ Mn 2+ activated CL in lunar plagioclases 4 o o 3 o 2 o 1 Luna µm

55 Synthetic doped feldspar samples (plagioclase An An 50 ) Mn 2+ intensity [counts] ppm 5000 ppm ppm wavelength [nm]

56 Luminescence activation 10 8 plagioclases alkali feldspar Intensity / a.u Mn content [ppm] rel. CL intensity mol-% Mn Intensity of the Mn 2+ activated CL in dependence on the Mn content in feldspar

57 Luminescence quenching emission excitation radiationless transition excitation activator activator luminescence emission concentration quenching

58 Conclusions

59 Conclusions As ideal crystal structures practically do not exist, the properties of minerals are determined by their real structure Luminescence spectroscopy may provide complex information about the defect structure of solids importance of spatially resolved spectroscopy There is a close relationship between specific conditions of mineral formation or alteration, the defect structure and the luminescence properties ( typomorphism ) problem of standardization For the interpretation of luminescence spectra it is necessary to consider several analytical and crystallographic factors, which influence the luminescence signal

Earth Materials I Crystal Structures

Earth Materials I Crystal Structures Isotopes same atomic number, different numbers of neutrons, different atomic mass. Ta ble 1-1. Su mmar y of quantu m num bers Name Symbol Values Principal n 1, 2,