Photon Factory Activity Report 2014 #32(2015) B

BL-10A/2013G127

Structural properties of (Al, H)-bearing bridgmanite, MgSi0.9Al0.1H0.1O3
1

T. Kuribayashi1, *, T. Inoue2, K. Fujino2 and T. Nagase3
Department of Earth Science, Graduate School of Science, Tohoku University, Sendai 980-8578
2GRC, Ehime University, Matsuyama 790-8577
3The Tohoku University Museum, Tohoku University, Sendai 980-8578

1. Introduction
Perovskite structured MgSiO3 was recently approved
by IMA-CNMNC as bridgmanite [1], although the phasehas been confirmed in a Tenham meteorite in 1997 [2].
Bridgmanite is regarded as one of main component
minerals in earth’s lower mantle, and would control its
various physical properties such as elasticity andelectromagnetism
Crystal structure of Mg-Pv belongs to the orthorhombic
system with space group of Pbnm (#62), and deviatesfrom the ideal cubic perovskite structure. The Mg-Pv
structure can include various minor components such as
Ca, Fe, Al, H and so on. Mg-Pv including a larger amountof Al and H was synthesized at the conditions of 25-26
GPa and ~1600ºC, and its incorporation mechanism (Si4+⇔ Al3+ + H+) is suggested [3]. However, structural detailon (Al, H)-bearing Mg-Pv is unknown, and is needed toinvestigate the behaviors of Al and H in Mg-Pv structure.
Single-crystal X-ray diffraction measurements on (Al,H)-bearing Mg-Pv was conducted to obtain its structuralinformation. In this report, we showed the brief results ofstructural refinement, and compared the polyhedral
properties of our sample with the previously reported
values of the perovskite structure with various chemicalformula.
2. Experimental ProcedureAlthough experimental details were already shown in
our last year report [4], we showed them again. Thesample used for this study was synthesized by [3] at 2526 GPa and ~1600ºC. The run product included (Al, H)bearing MgSiO3 phase, phase D, stishovite and quencheddendritic phase, which was liquid under high pressure andtemperature conditions. The chemical formula,
Mg0.976Si0.925Al0.094H0.089O3, of (Al, H)-bearing Mg-Pv wasverified by [3] with EDS-SEM and SIMS. After checking
the quality of crystals by taking oscillation photographs, asingle crystal of Al, H-bearing Mg-Pv (56 µm × 48 µm ×40 µm in size) was selected for synchrotron X-ray
diffraction experiments. Single crystal X-ray diffraction
experiments were performed using the automated fourcircle X-ray diffractometer installed at the beam line BL10A, Photon Factory, High Energy Accelerator Research
Organization. The wavelength (λ = 0.7129 Å) of
synchrotron radiation was calibrated by the unit cellvolume of the NIST ruby standard crystal at ambient
temperature. The unit cell parameters of Al, H-bearing
MgPv at room temperature were determined from 52

centered reflections in the 2 θ range between 11° and 35°.
The X-ray diffraction intensity data were collected up tosinθ/λ < 0.71 (2θmax = 60º) by using ω-scan method.
Structural refinement was conducted by using SHELXL
with WIN_GX software [5, 6]. The latest R and wR2
values are 3.8 % and 10.4 %, respectively.
3. Results and Discussion
The obtained lattice parameters of (Al, H)-bearing MgPv are as follows: a = 4.7890(18) Å, b = 4.954(2) Å and c= 6.924(6) Å. Table 1 shows several information of BO6
octahedron in Mg-Pv with various minor components.
The averaged B-O distances is 1.8010(17) Å, whilethat of A-O is 2.210(2) Å for 8-coordinates in (Al, H)bearing Mg-Pv. The mean distance of BO6 octahedron is
expanded 0.4% comparing with those of pure Mg-Pv[7].
It suggested that the B site should be occupied by Al and
Si. Also, the distance of 1.8010Å is the same as that of [8].
In the reference [8], the B-site is occupied by 92%Si and
8% Al. This result is in good agreement with our structurerefinement and chemical analysis. The octahedral site is akey to understand its incorporation mechanism.

Table 1.Information on lattice constant and BO6 octahedron of our (Al, H)-bearing Mg-Pv and the reference dataComposition
Unit Cell Parameters
abcV

3[Å ]This study(sample #1)
Mg0.98Si0.92Al0.09H0.09O3

Horiuchi et al.
(1987)
MgSiO3

Dobson & Jacobsen(2004)
MgSiO3

Vanpeteghem et al.
(2006)
Mg0.88Si0.92Al0.11Fe0.09O3

4.7890 (18)4.954 (2)6.924 (6)164.25 (7)4.7754 (3)*4.9292 (4)*6.8969 (5)*162.35 (2)*4.7780 (2)4.9298 (3)6.8990 (3)162.50 (1)4.7820 (1)4.9422 (2)6.9207 (3)163.561 (1)1.7922 (18)1.8023 (17)1.8086 (15)1.7827 (7)1.7960 (7)1.8005 (3)1.7952 (8)1.7998 (4)1.7829 (8)1.794 (1)1.799 (1)1.8126 (7)1.8010 (17)1.7931 (6)1.7930 (7)1.802 (1)BO6 Octahedron
B-O(2) [2]
B-O(2) [2]
B-O(1) [2]
Mean [6]*derived from [9]** lattice constants derived from [4]4. References[1] Tschauner et al., Science, 346, 1100-1102 (2014) [2]
Tomioka and Fujino, Science, 277, 1084-1086 (1997) [3]Inoue et al., in prep. (2015). [4] Kuribayashi et al., PFAR,
31, 299, (2014) .[5] Sheldrick (1997) [6] Farrugia LJ J.
Appl. Crystallogr., 32, 837-838 (1999) [7] Horiuchi et al.,Am. Mineral., 72, 357-360 (1987) [8] Vanpeteghem et al.,Phys. Ear. Planet. Interior., 155, 96-103 (2006) [9] Itoand Matsui, Ear. Planet. Sci. Lett., 38, 443-450 (1978)[10] Dobson and Jacobsen, Am. Mineral., 89, 807-811(2004).
* t-kuri@m.tohoku.ac.jp