1991 Fiscal Year Final Research Report Summary
Structural phase transformation of inorganic compounds under very high pressure studied by in-situ X-ray diffraction analysis
| Project/Area Number |
02403028
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
結晶学
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| Research Institution | Tohoku University |
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Principal Investigator |
SYONO Yasuhiko Tohoku University, Institute for Materials Research, Professor, 金属材料研究所, 教授 (80013481)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUCHI Masae Tohoku University, Institute for Materials Research, Associate Professor, 金属材料研究所, 助教授 (00005951)
FUJINAGA Yasuo Tohoku University, Institute for Materials Research, Research Associate, 金属材料研究所, 助手 (70005924)
KUSABA Keiji Tohoku University, Institute for Materials Research, Research Associate, 金属材料研究所, 助手 (60186385)
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| Project Period (FY) |
1990 – 1991
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| Keywords | X-ray diffraction / High pressure / Phase transformation / Compressibility / SrF_2 / Cubic anvil press / Oxides / Crystal chemistry |
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| Research Abstract |
An X-ray diffraction system has been combined with a 250 ton cubic-anvil type high pressure apparatus to make in-situ measurements of crystal structure, compressibility and phase equilibrium of pressure-induced phases of inorganic substance. The X-ray diffraction system consists of intense X-ray source of the rotating anode type (6OkV, 200mA), and solid state detector and pulse height analyzer system (2048 channels, 2627eV/channel). Both the X-ray source and goniometer carrying SSD are mounted on a common plate so as to make easier adjustment of optical path through pressure-medium composed of boron-epoxy lesin mixture. The d-specings of the diffraction peaks of NaCl which is used for pressure standard could be determined with an accuracy of <plus-minus> 0.1 %, which in turn warrants precision of (SY.+-.[) 0.1 GPa for the pressure calibration. B1-B2 transition of KCl was also detected at 2.1 GPa with a volume decrease of 13 %, in agreement with previous reports. Bulk moduli of B1 and B2 phase of KCl were also determined to be 18.2 <plus-minus> 0.2 and 21.5 <plus-minus> 1.1 GPa, respectively. Pressure-induced phase transition of SrF_2 was also studied up to 8GPa at room temperature. Fluorite structure was observed up to 5.8 GPa, where transformation to a PbCl_2 type took place. However, the high pressure phase remained down to 2.0 GPa with decreasing pressure, indicating a remarkable hysteresis. These observations suggest a martensitic mechanism of the fluorite-PbCl_2 type phase transition, which has been noted to be very sensitive to hydrostacity due to pressure medium. Bulk modili of SrF_2 with the fruorite and PbCl_2 type were determined to be 69.1 <plus-minus> 0.7 and 73.6 <plus-minus> 3.8 GPa respectively, in agreement with previous data. Along with the construction of insitu diffraction system, various investigations of phase transition in MO_2 and M_2O_3 were carried out at high pressure and temperatures, and crystallochemical implications were discussed.
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