Evolution of the local structure at Hf sites in SiHfOC upon ceramization of a hafnium-alkoxide-modified polysilsesquioxane: A perturbed angular correlation study
Cekić, Božidar Đ.
Koteski, Vasil J.
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The evolution of the environment of Hf sites in a hafnium-alkoxide-modified polysilsesquioxane upon polymer-to-ceramic transformation was investigated via the perturbed angular correlation (PAC) method. The results of the PAC measurements on samples thermally treated at temperatures from 400 to 1300 degrees C indicate that Hf is surrounded only by oxygen at all studied temperatures. This finding is in agreement with the evolution pathway of polymer-derived SiHfOC ceramics, which were reported to be generated as single-phase amorphous materials upon pyrolysis of alkoxide-modified polysiloxanes and subsequently to phase separate and crystallize towards HfO2/SiOC nanocomposites. Thus, the results presented here support our previous statement that there is a thermodynamic control on the phase separation and crystallization behavior of Si-M-O-C (M = metal) ceramics (Ionescu et al. 96;2013:1899-1903), which in the case of Hf leads to the precipitation and crystallization of hafnia nanopartic...les within a SiOC matrix. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords:Polymer-derived ceramics (PDCs) / Perturbed angular correlation (PAC) / HfO2/SiOC nanocomposites / Polymer-to-ceramic transformation / Nanostructure evolution
Source:Journal of the European Ceramic Society, 2015, 35, 1, 29-35
- Investigation of intermetallics and semiconductors and possible application in renewable energy sources (RS-171001)
- German Science Foundation (DFG) [DFG: IO 64/7-1]