1988 Fiscal Year Final Research Report Summary

STUDIES ON PHASE DIAGRAM AND TRANSFORMATION IN THIN FILMS OF ZIRCONIA ALLOYS

Research Project

Project/Area Number	62420046
Research Category	Grant-in-Aid for General Scientific Research (A)
Allocation Type	Single-year Grants
Research Field	金属材料(含表面処理・腐食防食)
Research Institution	TOHOKU UNIVERSITY
Principal Investigator	SUTO Hajime TOHOKU UNIVERSITY,professor, 工学部, 教授 (10005176)
Project Period (FY)	1987 – 1988
Keywords	CERIA / PRECIPITATION / SPUTTERING / THIN FILM / TRANSFORMATION / YTTRIA / 薄膜
Research Abstract	ZIRCONIA HAS POLYMORPHS OF CUBIC, TETRAGONAL AND MONOCLINIC PHASES FROM HIGH TO LOW TEMPERATURES. WHEN IT IS ALLOYED WITH YTTRIA, LIME OR MAGNESIA, THE HIGH TEMPERATURE PHASES ARE STABILIZED BY THE INTRODUCED OXYGEN VACANCIES. IT IS INTERESTING THAT ZIRCONIA IS STABILIZED BY CERIUM IN SPITE OF THE SAME VALENCE AS ZIRCONIUM. THE PRESENT INVESTIGATION CONSISTS OF TWO PARTS AS FOLLOWS. (1) THE PHASE DIAGRAM OF ZIRCONIA-CERIA SYSTEM WAS DECIDED EXPERIMENTALLY. THE ARCMELTED LOW CERIA ALLOYS WAS TETRAGONAL PHASE CONTAINING TRANSFORMATION TWINS AND DOMAINS LIKE LOW YTTRIA ALLOY, BUT COHERENT PRECIPITATION TAKES PLACE IN THE STEAD OF SPINODAL DECOMPOSITION. (2) THIN FILMS OF ZIRCONIA ALLOYS CONTAINING YTTRIA FROM 2 TO 8 MOL% WERE PREPARED BY MEANS OF RF-SPUTTERING. THE GRAIN SIZE WAS ABOUT 20 NM. THE TETRAGONAL PHASE IN 2 AND 2.5 MOL% YTTRIA ALLOYS WAS TRANSFORMED TO MONOCLINIC PHASE BY AGING AT 200 ゜C AGING, BUT CUBIC PHASE WAS STABLE TO THIS AGING.