caa a22 4500 388022353 CHVBK 20180307124928.0 cr unu---uuuuu 161130e199808 xx s 000 0 eng 10.1557/JMR.1998.0304 doi S0884291400045404 pii (NATIONALLICENCE)cambridge-10.1557/JMR.1998.0304 Metastability of tetragonal ZrO2 derived from Zr-n-propoxide-acetylacetone-water-isopropyl alcohol [Elektronische Daten] ZrO2 nanopowders derived from zirconium n-propoxide [Zr(OC3H7)4]-acetylacetone-water-isopropanol have been investigated with respect to their tetragonal metastability on heating-cooling processes. The transformation temperature of metastable tetragonal to monoclinic (t′ → m) phase is found to be governed by ultimate firing temperature, time, and atmospheres employed. Crystallite growth is fastened with increase in calcination temperatures over 1000-1400 °C, and the t′ → m transformation temperature is correlated linearly with crystallite size in the studied range of 12-20 nm. Heating in an oxygen environment increases the size of the final crystallites and hence the rate of the t′ → m transformation. It is revealed that the t′ → m transformation temperature depends largely on the heating atmosphere, but only weakly on the cooling one. Based on the findings of this work, surface oxygen deficiencies are attributed to be responsible for low-temperature tetragonal metastability. A crystallite growth model to explain the decline of t′-ZrO2phase is proposed. Kinetic and thermodynamic factors are also discussed in connection with the existing theories of tetragonal metastability. Copyright © Materials Research Society 1998 Zhan Zhaoqi Department of Chemical Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 Zeng Hua C. Department of Chemical Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 Journal of Materials Research Cambridge University Press 13/8(1998-08), 2174-2183 0884-2914 13:8<2174 1998 13 JMR https://doi.org/10.1557/JMR.1998.0304 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1557/JMR.1998.0304 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Zhan Zhaoqi Department of Chemical Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 NATIONALLICENCE 700 1- Zeng Hua C. Department of Chemical Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 NATIONALLICENCE 773 0- Journal of Materials Research Cambridge University Press 13/8(1998-08), 2174-2183 0884-2914 13:8<2174 1998 13 JMR CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge