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Time‐Resolved High and Low Temperature Phase Transitions of the Nanocrystalline Cubic Phase in the Y 2 O 3 ‐ZrO 2 and Fe 2 O 3 ‐ZrO 2 System
Author(s) -
Lajavardi Manouchehr,
Kenney Donald J.,
Lin Sheng Hsien
Publication year - 2000
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200000144
Subject(s) - nanocrystalline material , tetragonal crystal system , crystallite , monoclinic crystal system , cubic zirconia , analytical chemistry (journal) , phase (matter) , chemistry , cubic crystal system , crystallography , thermal decomposition , mineralogy , materials science , crystal structure , ceramic , organic chemistry , chromatography
The nanocrystalline cubic Phase of zirconia was found to be thermally stabilized by the addition of 2.56 to 17.65 mol % Y 2 O 3 (5.0 to 30.0 mol % Y, 95.0 to 70.0 mol % Zr cation content). The cubic phase of yttria stabilized zirconia was prepared by thermal decomposition of the hydroxides at 400°C for 1 hr. 2.56 mol % Y 2 O 3 ‐ZrO 2 was stable up to 800°C in an argon atmosphere. The samples with 4.17 to 17.65 mol % Y 2 O 3 were stable to 1200°C and higher. All samples at temperatures between 1450°C to 1700°C were cubic except the sample with 2.56 mol % Y 2 O 3 which was tetragonal. The crystallite sizes observed for the cubic phase ranged from 50 to 150 Å at temperatures below 900°C and varied from 600 to 800 nm between 1450°C and 1700°C. Control of furnace atmosphere is the main factor for obtaining the cubic phase of Y‐SZ at higher temperature. Nanocrystalline cubic Fe‐SZ (Iron Stabilized Zirconia) with crystallite sizes from 70 to 137 Å was also prepared at 400°C. It transformed isothermally at temperatures above 800°C to the tetragonal Fe‐SZ and ultimately to the monoclinic phase at 900°C. The addition of up to 30 mol % Fe(III) thermally stabilized the cubic phase above 800°C in argon. Higher mol % resulted in a separation of Fe 2 O 3 . The nanocrystalline cubic Fe‐SZ containing a minimum 20 mol % Fe (III) was found to have the greatest thermal stability. The particle size was a primary factor in determining cubic or tetragonal formation. The oxidation state of Fe in zirconia remained Fe 3+ . Fe‐SZ lattice parameters and rate of particle growth were observed to decrease with higher iron content. The thermal stability of Fe‐SZ is comparable with that of Ca‐SZ, Mg‐SZ and Mn‐SZ prepared by this method.