1993 Fiscal Year Final Research Report Summary
STUDY OF FERRIELASTICITY AND SUBLATTICE STRUCTURES
| Project/Area Number |
03452043
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
SAWADA Akiktsu OKAYAMA UNIVERSITY, FACULTY OF SCIENCE, PROFESSOR, 理学部, 教授 (30023154)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIHATA Yasuo OKAYAMA UNIVERSITY, FACULTY OF SCIENCE, ASSISTANT, 理学部, 助手 (90218181)
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| Project Period (FY) |
1991 – 1993
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| Keywords | ferrielasticity / ferridistortive crystal / sublattice strain / domain / order parameter / phase transition / ferrielasticity / structural phase transition |
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| Research Abstract |
(1) New concepts of "sublattice strain", "ferridistortive crystal" and "ferrielastics" have for the first time been defined on the basis of Landau theory(Ref.1)
(2) Single crystals of [N(CH3)4]2CoBr4 were grown and the temperature dependence of dielectric constants were measured from 10 K to 370 K.Anomolous temperature dependence, which cannot be expected in ordinary ferroelastics, were found. It is concluded that [N(CH3)4]2CoBr4 crystal is a ferridistortive crystal(Ref.2)
(3) Single crystals of [P(CH3)4]2CoBr4, which has P atoms instead of N atoms in [N(CH3)4]2CoBr4, were grown, and studied by optical and dielectric methods. It has been found that the transition temperature Tc is raised by 80 K, and the transition is of the first order and the deviation of the monoclinic angle from 90 takes negative values in the temperature range from 20 K to 400 K.It is concluded that the two kinds of cations play a major role, while the anion a minor role in the ferridistortive phase transition in [A(CH3)4]2XBr4-type crystals(Ref.5)
(4) Domain patterns in [N(CH3)4]2ZnBr4 single crystals were studied with a polarizing microscope and video-tape recorder and image analyzer. It has been found that a-domains do not vanish, but ac-rectangullar domains change their brightness just at the temperature Tz where the monoclinic angle happens to be 90. This is the first observation of the compensation temperature Tz by optical method(Ref.6)
(5) The above results were reported in the international meeting on domains whichi were held in 1992 in France, and in the international meeting on ferroelectricity which were held in 1993 in USA.
(6) The field of ferrielasticity will be developed and found to be very important in elastisity in general.
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