1987 Fiscal Year Final Research Report Summary
EXPERIMENTAL STUDY ON KINETICS OF DISCOMMENSURATION IN FERROELECTRIC MATERIALS
| Project/Area Number |
61540239
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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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 | YAMAGUCHI UNIVERSITY, FACULTY OF SCIENCE |
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Principal Investigator |
MASHIYAMA HIROYUKI FACULTY OF SCIENCE, YAMAGUCHI UNIVERSITY, 理学部, 助教授 (20091209)
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| Co-Investigator(Kenkyū-buntansha) |
KASANO HIRONOBU FACULTY OF SCIENCE, YAMAGUCHI UNIVERSITY, 理学部, 助手 (00183260)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Ferroelectrics / Incommensurate Phase / Commensurate Phase / Kinetics of Phase Transition / Discommensuration / Pinning / 緩和過程 |
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| Research Abstract |
THE KINETICS OF THE INCOMMENSURATE-COMMENSURATE PHASE TRANSITION IN FERROELECTRIC MATERIALS HAS BEEN RECENTLY INTERESTED. IN A_2 BX_4-TYPE MATERIALS, SIX DISCOMMENSURATIONS WHICH SEPARATE MICROSOPIC DOMAINS ARE CREATED OR ANNIHILATED SIMULTANEOUSLY WHEN THEY GET AN ACTIVATION ENERGY. THE TIME EVOLUTION HAS BEEN PREDICTED THEORETICALLY TO OBEY A LOGARITHMIC LAW.
WE MEASURED THE DIELECTRIC CONSTANT AND X-RAY SATELLITE REFLECTION OF K_2ZnCl_4 IN WHICH THE TIME DEPENDENCE IS VERY SLOW BECAUSE OF IMPURITIES OR IMPERFECTIONS IN THE CRYSTAL. WHEN THE TEMPERATURE WAS CHANGED FROM THE COMMENSURATE PHASE TO THE INCOMMENSURATE PHASE (VICE VERSA OR EVEN WITHIN THE INCOMMENSURATE PHASE), THE MEAN DISTANCE BETWEEN DISCOMMENSURATIONS APPROACHES TO ITS EQUILIBRIUM VALUE WITH AN EXPONENTIAL DECAY AT THE EARLIER STAGE, AND WITH THE LOGARITHMIC ONE AT THE LATER STAGE, IN QUALITATIVE AGREEMENT WITH THE THEORY.
WE ALSO TRIED TO OBSERVE THE KINETIC PROCESS DIRECTLY BY TAKING HIGHLY RESOLVED ELECTRON MICROSCOPIC PHOTOGRAPHS. THE EXPERIMENT IS STILL IN PROGRESS, HOWEVER, WE COULD RECOGNIZE THE TRIPLE LATTICE CELLS OF THE COMMENSURATE PHASE OF K_2ZnCl_4 AND THE LATTICE DISTORTION WHICH MAY BE RELATED TO THE TERMINAL POINT OF DISCOMMENSURATIONS.
THE X-RAY STRUCTURAL ANAlYSES OF HIGH-ORDERCOMMENSURATE STRUCTURE IN LiRbSO_4, TETRAMETHYLAMMONIUM SALTS AND OTHERS HAVE BEEN PERFORMED TO CLARIFY THE CRYSTAL STURCTURE OF DISCCOMENSURATIONS. THE DISCOMMENSURATION OF THE NINEFOLD COMMENSURATE PHASE IN THIOUREA WAS WELL DEFINED; IT IS THE PARAELECTRIC STRUCTURE LOCALLY WHOSE WIDTH IS RATHER NARROWER THAN TWO TIMES OF THE BASIC LATTICE PERIOD, AND SEPARATES THE MICROSCOPIC EFRROELECTRIC DOMAINS.
WE HAVE BEEN STUDYING THE INCOMMENSURATE-COMMENSURATE PHASE TRANSITION IN RELATED MATERIALS.
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