Topic
Tridymite
About: Tridymite is a research topic. Over the lifetime, 840 publications have been published within this topic receiving 14831 citations.
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TL;DR: In this article, a model of a six-membered ring in which bulky thallium atoms find their place is presented, which is related to the stuffed tridymite structural type of monophosphate TlBeAsO 4.
12 citations
TL;DR: In this article, a water assisted phase transformation process from crystalized AlPO4-5 to AlPO 4-tridymite was studied by the combination of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and in situ multinuclear MAS NMR.
12 citations
TL;DR: Browneite (IMA 2012-008), MnS, is a new member of the sphalerite group, discovered in Zaklodzie, an ungrouped enstatite-rich achondrite as discussed by the authors.
Abstract: Browneite (IMA 2012-008), MnS, is a new member of the sphalerite group, discovered in Zaklodzie, an ungrouped enstatite-rich achondrite The type material occurs as one single crystal (~16 μm in size) in contact with and surrounded by plagioclase; enstatite and troilite are nearby Low-Ni iron, martensitic iron, tridymite, quartz, cristobalite, sinoite, schreibersite, buseckite, keilite, and graphite, are also present in the type sample Browneite is yellowish brown and translucent The mean chemical composition, as determined by electron microprobe analysis of the type material, is (wt%) S 3646, Mn 6231, Fe 062, Ca 010, sum 9949, leading to an empirical formula calculated on the basis of 2 atoms of (Mn_(0993)Fe_(0010)Ca_(0002))S_(0995) Electron back-scatter diffraction patterns of browneite are a good match to that of synthetic β-MnS with the F43m structure, showing ɑ = 5601 A, V = 17571 A^3, and Z = 4 Browneite is a low-temperature (<200 °C) phase, metastable relative to alabandite, that postdates the impact melting and subsequent crystallization of an enstatite-rich rock
12 citations
TL;DR: In this paper, the activation energy in the quenching process was evaluated by a least-squares fitting of the Arrhenius plots, assuming the Mott-Seitz model, assuming that the energy of non-radiative transition in this process might be transferred to lattice vibrations as phonons in two different manners.
Abstract: Cathodoluminescence (CL) spectra of tridymite and cristobalite have broad peaks around 430 and 400 nm, respectively, both of which can be assigned to the [AlO 4 /M + ] 0 defect. The CL intensities of these spectral peaks in the blue region decrease with prolonged exposure to electron irradiation, similar to the short-lived luminescence observed in quartz, although quartz shows a lower decrease in CL intensity compared to these minerals. Cristobalite has a higher CL intensity reduction rate during irradiation than does tridymite. Irradiation of these minerals at low temperatures results in a more rapid decay of CL emission, whereas that of quartz shows no apparent change in the rate of CL emission at similar temperatures. Confocal micro-Raman spectroscopy of the electron irradiated surface of these minerals reveals the amorphization caused by the interaction of the electron beam with the surface layer to a depth of several micrometers. This suggests that such structural destruction diminishes the activity of CL emission centers related to the [AlO 4 /M + ] 0 defects by migration of monovalent cations associated with exchanged Al in the tetrahedral sites. Both samples present a considerable reduction of their CL intensities at higher temperature, suggesting a temperature quenching phenomenon. The activation energy in the quenching process was evaluated by a least-squares fitting of the Arrhenius plots, assuming the Mott-Seitz model. The result implies that the energy of non-radiative transition in this process might be transferred to lattice vibrations as phonons in two different manners. This might be related to different irradiation responses of the CL with a change in sample temperature.
12 citations