Laser-induced thermal characterization of nano Ag metal dispersed ceramic alumina matrix Sajan. D. George 1* , Aji A Anapara 2 , K. G. K Warrier 2 , P.Radhakrishnan 1 , C. P. G. Vallabhan 1 and V. P. N. Nampoori 1 1 International School of Photonics, Cochin University of Science and Technology Kochi, India – 682 022 2 Ceramic Technology Division, Regional Research Laboratory, CSIR, Thiruvananthapuram, India – 695 019 ABSTRACT In this paper, we report the measurements of thermal diffusivity of nano Ag metal dispersed ceramic alumina matrix sintered at different temperatures using laser induced non-destructive photoacoustic technique. Measurements of thermal diffusivity also have been carried out on specimens with various concentration of nano metal. Analysis of the data is done on the basis of one-dimensional model of Rosencwaig and Gersho. The present measurements on the thermal diffusivity of nano metal dispersed ceramic alumina shows that porosity has a great influence on the heat transport and the thermal diffusivity value. The present analysis also shows that the inclusion of nano metal into ceramic matrix increases its interconnectivity and hence the thermal diffusivity value. The present study on the samples sintered at different temperature shows that the porosity of the ceramics varies considerably with the change in sintering temperature. The results are interpreted in terms of phonon assisted heat transfer mechanism and the exclusion of pores with the increase in sintering temperature. Keywords: Photoacoustic, sol-gel, ceramics, thermal properties, nano composite INTRODUCTION Ceramic materials play a very important role in the fabrication of electronic and optoelectronic devices. Ceramic alumina is considered to be an ideal candidate for the optical, thermal and structural applications due to its special properties such as tunable electrical properties, toughness, high temperature tolerance, light weight and excellent resistance against corrosion and wear [1-2]. The thermal properties of these ceramics are basically determined by their composition and structure. It is the rate of heat diffusion that essentially determines the thermal shock resistance of brittle solids such as ceramics. In such materials, thermal accumulation causes thermal induced stresses in the sample, which in turn causes catastrophic failure and deterioration in ceramic-based devices. The thermal shock resistance of the ceramics can be improved by the incorporation of a metal with high thermal conductivity value into the ceramic matrix [3]. In the recent years, fabrication of nano metal dispersed ceramics has gained much attention due to its excellent structural and electrical properties. In addition, these materials posses excellent chemical inertness, good oxidation resistance and an enhanced toughness. It has been observed that the nano metal dispersed ceramics exhibit different thermal characteristics compared to the intrinsic bulk specimen. Thermal diffusivity value is an important thermophysical parameter in this context, as this quantity determines the heat propagation and thermal shock resistance in these materials. During the last two decades, the non destructive and non intrusive laser induced photothermal methods have emerged as an effective research and analytical tool for characterizing the thermal, optical and transport properties of a variety of materials such as ceramics, liquid crystals, semiconductors etc [4-8]. All these photothermal methods are based on the detection, by one means or other, of a transient temperature change that characterizes the thermal waves generated in the sample due to the nonradiative deexcitation followed by an intensity modulated optical excitation. In the simple and elegant photoacoustic (PA) technique, these periodic thermal waves causes density fluctuation in the sample and in the coupling medium. *sajan@cusat.ac.in, International School of Photonics, Cochin University of Science and Technology, Kochi, India –682 022 Nanotechnology, Robert Vajtai, Xavier Aymerich, Laszlo B. Kish, Angel Rubio, Editors, Proceedings of SPIE Vol. 5118 (2003) © 2003 SPIE · 0277-786X/03/$15.00 207