- 作者: Manouchehr Lajavardia,b, Donald J. Kenneya,c and Sheng Hsien Lind
- 中文摘要:
The nanocrystalline cubic Phase of zirconia was found to be thermally stabilized by the addition of 2.56 to 17.65 mol % Y2O3 (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 % Y2O3-ZrO2 was stable up to 800 °C in an argon atmosphere. The samples with 4.17 to 17.65 mol % Y2O3 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 % Y2O3 which was tetragonal. The crystallite sizes observed for the cubic phase ranged from 50 to 150 A 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 A 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 Fe2O3. 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 Fe3+. 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. - 英文摘要: --
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