Structural changes and oxidation of ferroan phlogopite with increasing temperature: in situ neutron powder diffraction and Fourier transform infrared spectroscopy

Chon, Chul Min; Lee, Chul Kyoo; Song, Yungoo; Kim, Sin Ae

doi:10.1007/s00269-005-0045-y

Cited by 22 publications

(17 citation statements)

References 21 publications

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“…2e, 7b, and 8b) is not caused by pure changes in absorption coefficients, but instead is more likely due to the orientation of OH dipoles, which turns away from the (001) direction. As a result, the absorption projected on the sheet layer increases, and the total effect is that the band height shows a weaker decrease in relation to the value below 600 K. Our data are basically consistent with the observations by the neutron diffraction work of Chon et al (2006), which showed an alteration of OH orientation of phlogopite on heating. The results also show that the environments around the proton (H + ) as well as OH bonds are more affected by heating as compared to other phonons.…”

Section: Discussionsupporting

confidence: 82%

“…2e, 3b, and 8b). This appears to suggest that in addition to a distortion of MO 6 octahedra, TO 4 (T = Si, Al) tetrahedra and OH modes are also responsible for, or involved in, the previously reported local structural change (e.g., Chon et al 2006;Tutti and Lazor 2008). Considering the change in OH bonds and the lattice vibrations of the framework, we believe that there is a connection between structural change or so-called phase transition near 600 K and the change of OH dipole orientation, which both occurred near 600-700 K. What is more, it is the OH-related bands that showed significant abnormality (Fig.…”

Section: Discussionmentioning

confidence: 93%

“…Changes in orientations of OH dipoles were reported in 2M 1 -phengite (a dioctahedral mica) on heating (Mookherjee et al 2001). Neutron diffraction data reported by Chon et al (2006) showed that the angle between the OH vector and the (001) plane in phlogopite started to decease (i.e., OH dipole turned away from the [001] direction) in a nonlinear manner from about 600-700 K. As a result of the change in OH dipole orientation, its project on the (001) plane may change and this affects the measured absorption. This may also account for the abnormal temperature dependence of the OH libration and stretching bands (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…Anikin (1971) reported a second-order phase transition near 563 K. Egorov et al (1972) suggested an increase in thermal conductivity in [001] direction in phlogopite at temperatures above 573 K (or 673 K for fluorphlogopite), and attributed the change to the expansion of Mg octahedra during heating and rotation of a tetrahedral grid from ditrigonal toward hexagonal. The X-ray diffraction work of Takeda and Morosin (1975) showed a clear break of temperature dependence for cell parameters a and b in a synthetic fluorphlogopite near 673 K. Results from in situ neutron powder diffraction (Chon et al 2006) showed that the expansion rate of unit-cell parameters for ferroan phlogopite varied discontinuously, with a break at a much higher temperature (773 K), which is considered to be due to a distortion of MO 6 octahedra, a decrease in mean <M-O> distance, and an increase in octahedral flattening angle. Chon et al (2006) attribute these changes to Fe oxidation and dehydroxylation processes, however.…”

Section: Introductionmentioning

confidence: 99%

“…The X-ray diffraction work of Takeda and Morosin (1975) showed a clear break of temperature dependence for cell parameters a and b in a synthetic fluorphlogopite near 673 K. Results from in situ neutron powder diffraction (Chon et al 2006) showed that the expansion rate of unit-cell parameters for ferroan phlogopite varied discontinuously, with a break at a much higher temperature (773 K), which is considered to be due to a distortion of MO 6 octahedra, a decrease in mean <M-O> distance, and an increase in octahedral flattening angle. Chon et al (2006) attribute these changes to Fe oxidation and dehydroxylation processes, however. The recent Raman study by Tutti and Lazor (2008) reported discontinuities in Raman frequencies as a function of temperature near 638 ± 15 K and suggested deformation and elongation of Mg octahedra along the crystallographic c-axis.…”

Section: Introductionmentioning

confidence: 99%

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Optical phonons, OH vibrations, and structural modifications of phlogopite at high temperatures: An in-situ infrared spectroscopic study

Zhang

Tarantino

et al. 2016

American Mineralogist

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The thermal behavior of optical phonons and OH vibrations of phlogopite (a trioctahedral mica) was examined at temperatures up to 1000 K using in situ infrared spectroscopy. The results showed that with increasing temperature, O-K bands in phlogopite exhibited a relatively strong variation in frequency in a manner similar to those in muscovite. The work revealed that different types of OH bands (fundamentals and combinations) have very different thermal behavior or temperature dependence, and their absorption coefficients are commonly not constant on heating. OH combination bands that are associated with summation processes of multi-phonon interactions commonly show a decrease in their intensities on heating, but in contrast combination bands due to difference processes generally exhibit an increase. This means that temperature dependencies of their absorption coefficients need to be considered when using the Beer-Lambert law to determine or estimate OH contents or hydrogen concentrations at high temperatures. The results showed a structural anomaly associated with a discontinuity in the temperature derivative of the wavenumber of Al-O and Si-O vibrations and O-H stretching near 600 K. However, framework-related phonon modes in the FIR and MIR regions do not suggest a break of the original monoclinic structural symmetry in the investigated temperature region. The complex changes are attributed to temperature-induced alteration of local configuration involving TO 4 tetrahedra and a possible change of the orientation of OH dipoles, in addition to a previously reported distortion of MO 6 octahedra. Increasing temperature to 1000 K also causes partial dehydroxylation, as evidenced by the disappearance of the OH band near 3623 cm -1 and the decrease in OH band height and area of other OH bands. The study did not record the formation of H 2 O inside phlogopite as a result of partial dehydroxylation. The work offers new data and findings that have important implications in understanding the complex structural modifications and the behavior of phonon modes and the thermal stability of hydroxyls on approaching the dehydroxylation, as well as the way hydrogen is released from micas at high temperatures. Our data also show that phologpite becomes less transparent with increasing temperature suggesting a change of radiative properties and ability to transmit heat, which could be of interest for modeling thermal-transmission in crustal rocks.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 93%