Assessment of quality of quartz crystals by EPR and γ-ray diffraction

Nienhaus, Karin; Stegger, P.; Lehmann, Gerhard; Schneider, J. R.

doi:10.1016/0022-0248(86)90130-2

Cited by 8 publications

(4 citation statements)

References 10 publications

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“…the variation of the resonant field B, with the angle CI between c-axis and field direction. This proportionality was observed for Fe3+ in quartz [3] and calcite [4].…”

Section: Mosaic Structuresupporting

confidence: 62%

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Characterization of the Crystal Quality of Calcites by Electron Paramagnetic Resonance

Vassilikou‐Dova

1993

Physica Status Solidi (b)

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The linewidths B,, and anisotropies in the electron paramagnetic resonance spectra of MnZ + impurities are measured in calcite single crystals and used for the determination of the origin of line broadening. Two different mechanisms of broadening, structural and chemical, are distinguished. From the differing angular dependences of the observed linewidths, large differences in the crystal quality are inferred.The differences in quality are also apparent in the EPR spectra of powder calcites, but no information about the mechanisms can be obtained. I ) Panepistimiopolis, Zografos, GR-15784 Athens, Greece.

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“…the variation of the resonant field B, with the angle CI between c-axis and field direction. This proportionality was observed for Fe3+ in quartz [3] and calcite [4].…”

Section: Mosaic Structuresupporting

confidence: 62%

“…These distortions were shown to be very small in crystals of normal quality [3], but are expected to increase with the content of (diamagnetic or paramagnetic) impurities of the crystals and size mismatch between host and impurity ions.…”

Section: Introductionmentioning

confidence: 97%

Characterization of the Crystal Quality of Calcites by Electron Paramagnetic Resonance

Vassilikou‐Dova

1993

Physica Status Solidi (b)

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“…All these crystals were of comparably high quality as shown by the low linewidths of their EPR signals from Fe 3+ at low temperatures (Nienhaus et al 1986). Depending on the seed orientation of the synthetic crystals either the I or the S centers dominated.…”

Section: Methodsmentioning

confidence: 96%

“…Investigation of natural amethysts and hydrothermally grown synthetic iron-doped quartz of unusually high quality (Nienhaus et al 1986) in combination with exchange of monovalent cations by high-temperature electrolysis allowed identification of the alkali ion and analysis of its hfs tensor in the $1 center. The previous uncertainties in the analysis and interpretation of the 57Fe hfs (Becker and Lehmann 1980) could also be removed.…”

Section: Introductionmentioning

confidence: 99%

The structures of three centers of trivalent iron in ?-quartz

Stegger

Lehmann

1989

Phys Chem Minerals

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Abstract. Trivalent iron is known to occur in amethysts in three different environments: substitutional with an as yet unidentified alkali ion in an adjacent interstitial site on the twofold axis (so-called $1 center), substitutional with a proton on one of the four oxygen neighbors ($2 center) and without detectable charge compensation (so-called I center because it was proposed to be in interstitial sites, but its nature is still disputed). The alkali ion in the Sz center was now identified as Li and the Li and Fe superhyperfine (shf) tensors were determined by electron paramagnetic resonance at low temperatures in samples of unusually high quality. The fine structure and ~H shf structure tensors for the $2 center with the proton on an oxygen with longer bond distance were evaluated and the geometry of the oxygen coordination was estimated by application of the superposition model. For the I center the 57Fe and zgsi shf splittings were determined and the evidence in favor of assignment to an interstitial site is reviewed.

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Dynamic Effects in a New Substitutional Center of Trivalent Iron in Quartz

Stegger

Lehmann

1989

Physica Status Solidi (b)

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After exchange of Li against Na in a natural quartz of high quality by electrolysis a t higher temperatures a new center of Fe3+ with monoclinic site symmetry a t room temperature is detected by electron paramagnetic resonance (EPR). At temperatures below 200 K the linewidths of the EPR spectra increase considerably, and a t about 60 K a signal of a triclinic center with a wellresolved quartet hyperfine splitting appears instead. Thus the charge-compensating Na ion evidently changes rapidly between two equivalent positions a t higher temperatures. An estimate of the activation energy for this hopping process is obtained from the temperature dependence of the linewidths for the monoclinic spectrum. Nach Austausch von Li gegen Na in einem naturlichen Quarz hoher Qualitkit durch Elektrolyse bei hoheren Temperaturen wird ein neues Zentrum des dreiwertigen Eisens mit monokliner Punktsymmetrie bei Raumtemperatur durch Elektronenspinresonanz (EPR) entdeckt. Unterhalb200 K nehmen die Linienbreiten seiner EPR-Spektren stetig zu, und bei ca. 60 K taucht ein Signal eines triklinen Zentrums mit gut aufgeloster Quartett-Hyperfeinaufspaltung auf. Na+ als Ladungskompensator springt offenbar schnell zwischen zwei Lquivalenten Positionen bei hoheren Temperaturen. Die Aktivierungsenergie fur diesen Sprung kann aus der Temperaturabhkngigkeit der Linienbreiten fur das monokline Zentrum abgeschkitzt werden.

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Assessment of quality of quartz crystals by EPR and γ-ray diffraction

Cited by 8 publications

References 10 publications

Characterization of the Crystal Quality of Calcites by Electron Paramagnetic Resonance

Characterization of the Crystal Quality of Calcites by Electron Paramagnetic Resonance

The structures of three centers of trivalent iron in ?-quartz

Dynamic Effects in a New Substitutional Center of Trivalent Iron in Quartz

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