Enhanced Kinetic Stability of Pure and Y-Doped Tetragonal ZrO2

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• 作者：Michaela Kogler ; Eva-Maria K枚ck ; Stefan Vanicek ; Daniela Schmidmair ; Thomas G枚tsch ; Michael St枚ger-Pollach ; Clivia Hejny ; Bernhard Kl枚tzer ; Simon Penner
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：December 15, 2014
• 年：2014
• 卷：53
• 期：24
• 页码：13247-13257
• 全文大小：659K
• ISSN：1520-510X

文摘

The kinetic stability of pure and yttrium-doped tetragonal zirconia (ZrO₂) polymorphs prepared via a pathway involving decomposition of pure zirconium and zirconium + yttrium isopropoxide is reported. Following this preparation routine, high surface area, pure, and structurally stable polymorphic modifications of pure and Y-doped tetragonal zirconia are obtained in a fast and reproducible way. Combined analytical high-resolution in situ transmission electron microscopy, high-temperature X-ray diffraction, and chemical and thermogravimetric analyses reveals that the thermal stability of the pure tetragonal ZrO₂ structure is very much dominated by kinetic effects. Tetragonal ZrO₂ crystallizes at 400 掳C from an amorphous ZrO₂ precursor state and persists in the further substantial transformation into the thermodynamically more stable monoclinic modification at higher temperatures at fast heating rates. Lower heating rates favor the formation of an increasing amount of monoclinic phase in the product mixture, especially in the temperature region near 600 掳C and during/after recooling. If the heat treatment is restricted to 400 掳C even under moist conditions, the tetragonal phase is permanently stable, regardless of the heating or cooling rate and, as such, can be used as pure catalyst support. In contrast, the corresponding Y-doped tetragonal ZrO₂ phase retains its structure independent of the heating or cooling rate or reaction environment. Pure tetragonal ZrO₂ can now be obtained in a structurally stable form, allowing its structural, chemical, or catalytic characterization without in-parallel triggering of unwanted phase transformations, at least if the annealing or reaction temperature is restricted to T 鈮?400 掳C.