Cathodoluminescence characterization of enstatite

Abstract

Enstatite in meteorite shows various emissions of cathodoluminescence (CL), and CL emission in terrestrial enstatite has been confirmed in this study. The CL spectra of these enstatite exhibit two broad emission bands at around 400 nm in a blue region and at around 670 nm in a red region. The emission components obtained by a spectral deconvolution can be assigned to impurity centers of Cr 3+ (1.70-1.75 eV) and Mn 2+ (1.85-1.90 eV) and to three defect centers (2.72-2.75, 3.18, and 3.87 eV). The emission component at 3.18 eV might be associated to the defect center derived from structural distortion by the substitution of Al for Si in a tetrahedral site. Extraterrestrial enstatite gives a characteristic emission at 3.87 eV in a blue to UV region, which is not detected in the terrestrial enstatite, suggesting radiation-induced defect by cosmic rays.

Cathodoluminescence color zonation in the Antarctic meteorite (enstatite chondrite) of Yamato 86004

“…All of them have two broad emission bands at around 400 nm in a blue region and at around 670 nm in a red region. Spectral deconvolution of the CL using a Gaussian curve fitting were carried out to clarify the emission components derived from various emission centers by the method proposed by Ohgo et al (2015). The results of the spectral deconvolution reveal five emission components in their spectra (Figs.…”

“…According to Ohgo et al (2015), the component at 2.73 eV can be assigned to an emission center (Defect I) related to 'intrinsic defect' formed during crystal growth. Such defect center has been detected in synthetic enstatite without any activator and quencher ions (e.g., Lofgren and Dehart, 1992).…”

“…Furthermore, forsterite has emission components of Cr 3+ ion at 1.65-1.72 eV, Mn 2+ ion at 1.92 eV, defect center at 2.75 and 3.15 eV (Gucsik et al, 2012), all of which accord closely with corresponding components obtained from the CL spectra of the enstatite in zone 1, 2 and 3. Ohgo et al, (2015) presumed that the emission component at 3.13-3.15 eV might be due to the defect center (Defect II) related to structural distortion of T(Si, Al)-O chain when Al substitutes for Si and/or deformation of the lattice due to an incorporation of Ca and Ti ions. In the case of measured enstatite, however, too low concentrations of Ca and Ti makes more difficult to judge the effect of impurity elements on the lattice in the enstatite (Table 1).…”

“…In the case of measured enstatite, however, too low concentrations of Ca and Ti makes more difficult to judge the effect of impurity elements on the lattice in the enstatite (Table 1). According to Ohgo et al (2015), the emission component at 3.77 eV in zone 1-3 enstatite might be related to the defect center (Defect III) attributable to cosmic-ray irradiation on the surface of the parent body and during traveling in space. Cosmic rays with high energy could flick out oxygen in enstatite crystal structure and form oxygen vacancy related to defect center with a near-UV emission.…”

“…This result is also supported by the peak energy of the emission component related to Mn 2+ impurity. According to Ohgo et al (2015), CL feature of red emission is useful to distinguish between Oen and LT-Cen phases. In the terrestrial enstatite, Oen has an emission component of impurity Mn 2+ ion at 1.85 eV, but at 1.90 eV for LT-Cen.…”