CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 5281–5286 Synthesis and optical limiting effects in ZrO 2 and ZrO 2 @SiO 2 core–shell nanostructures K. Mani Rahulan a,n , G. Vinitha b , L. Devaraj Stephen a , Charles Christopher Kanakam a a Department of Chemistry, SRM Valliammai Engineering College, Kattankulathur, Chennai, India b Department of Physics, VIT University, Chennai, India Received 15 October 2012; received in revised form 30 November 2012; accepted 9 December 2012 Available online 20 December 2012 Abstract ZrO 2 nanoparticles were synthesized by the chemical precipitation method and coated with silica through seeded polymerization technique to form core–shell type ZrO 2 @SiO 2 nanostructures. The structural, morphological and silica coating formation of the bare and silica coated particles were studied using Transmission electron microscopy, X-ray diffraction and Fourier Transform Infrared Spectroscopy. Thermogravimetric analysis and Zeta potential measurements were performed to check the thermal and dispersion stability of the nanostructures. The optical limiting performance of these nanostructures was studied using open-aperture Z-scan technique in which nanosecond laser pulses at 532 nm have been used for optical excitation. Both bare and silica coated ZrO 2 nanoparticles exhibited good optical limiting behavior due to excited state absorption, arising from effective three photon absorption. It is observed that the optical nonlinearity is enhanced in core shell structures as compared with the bare particles. & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Core–shell nanoparticles; Stober method; X-ray diffraction; Optical limiting 1. Introduction Zirconia (ZrO 2 ) nanoparticles have attracted much interest due to their enhanced optical and electrical proper- ties with applications as piezoelectric, electro-optic and dielectric material [1]. Because of their obvious improve- ment in hardness, wear resistance, and thermal shock resistance, ZrO 2 has turned into a technologically promis- ing ceramic material of the current generation. The approach for designing and fabricating such material in a core–shell model has attracted considerable attention because these nanoparticles with a well defined core and shell structures often exhibit improved physical and che- mical properties over their single component counterparts. A variety of methods have been demonstrated for the preparation of nanoparticles in a core–shell model during the past decades. Some investigators reported that such particles could be prepared by encapsulation of inorganic particles in a polymer shell [2,3]. Mohamed El-Toni et al. reported novel silica coating of titania nanoparticles by seeded polymerization technique with optimization of coating parameters to obtain a dense silica coating for titania nanoparticles [4]. The formation of silica coating layers on ZrO 2 is important in a broader range of applications. The uniformly coated shell provides enhance- ment to the core along with passivation and extra func- tionalities. An appropriate shell layer can protect the core metal from the damage of high energy laser pulses, improve resistance to possible chemical reactions of the metal with its environment and even modify the electrical and optical properties of nanoparticles. In this study, core–shell type ZrO 2 and ZrO 2 @SiO 2 nanoparticles were synthesized through the combination of chemical precipitation method and seeded polymerization approach. The structural and morphology of these nano- composites were characterized by using various advanced techniques such as transmission electron microscopy (TEM) and X-ray diffractometer (XRD). The interactions and framework substitution between core and shell com- ponents are then measured by using Fourier transform www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2012.12.029 n Corresponding author. Tel./fax: þ91 97 91012149. E-mail addresses: krahul.au@gmail.com (K. Mani Rahulan), charlesckin@yahoo.com (C.C. Kanakam).