Journal of Thermal Analysis and Calorimetry, Vol. 76 (2004) 43–48 EMANATION THERMAL ANALYSIS STUDY OF A SOL–GEL PRECURSOR FOR SILICA–TITANIA WAVEGUIDES V. Balek *1 , Z. Málek 1 , J. Šubrt 2 , M. Guglielmi 3 , P. Innozenzi 3 , V. Rigato 4 and G. Della Mea 4 1 Nuclear Research Institute Øe plc, CZ-250 68 Øe, Czech Republic 2 Institute of Inorganic Chemistry ASCR, 250 68 Øe, Czech Republic 3 Department of Mechanical Engineering, University of Padova, 35131 Padova, Italy 4 I.N.F.N., Legnaro National Laboratories, 35020 Legnaro, Italy Abstract Emanation Thermal Analysis (ETA) was demonstrated as a tool for the characterization of micro- structure changes of a sol–gel precursor for silica–titania layers deposited on the glass plate to be used as planar waveguides. Temperature ranges of 280–330 and 380–500°C, respectively, in which the densification of the layers took place, were determined by ETA under in situ conditions of the sample heating. Results of thermogravimetry were compared with the ETA data. Keywords: densification, emanation thermal analysis, planar waveguides, silica–titania layers, sol–gel Introduction By means of the sol–gel technique the silica based planar waveguides with low losses were prepared. When using the sol–gel processing the refractive index may be controlled by the composition of the starting solution of titanium alkoxides and other suitable pre- cursors [1–3]. SiO 2 –TiO 2 sol–gel films have been widely used as planar waveguides be- cause of the easy tunability of the refractive index and losses lower than 1 dB cm –1 [4]. In the preparation of planar waveguides deposited on the substrate by the sol–gel technique, the thermal treatment of the intermediate products is frequently used with the aim to obtain well-consolidated (dense) layers. Methods making possible to charac- terize the microstructure evolution of coatings are, therefore, of interest in this field. In this study the emanation thermal analysis (ETA) [5–7] was used to character- ize the microstructure development of the sol–gel silica titania layers to be used as optical waveguides. In our previous studies the ETA was already applied to charac- terize the thermal behavior of titania based materials as powders [8] and sol–gel pre- pared thin films [9]. This method monitored the development of surfaces and sub- surfaces microstructure during the preparation of adsorbents and catalysts on heating 1388–6150/2004/ $ 20.00 © 2004 Akadémiai Kiadó, Budapest Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht * Author for correspondence: E-mail: bal@ujv.cz