Hyperfine Interact (2010) 197:239–243 DOI 10.1007/s10751-010-0220-5 Electric quadrupole interactions in nano-structured SnO 2 as measured with PAC spectroscopy J. M. Ramos · A. W. Carbonari · M. S. Costa · R. N. Saxena Published online: 24 November 2010 © Springer Science+Business Media B.V. 2010 Abstract Measurements of the electric quadrupole interaction were used to char- acterize pure and cobalt-doped samples of SnO 2 prepared by the sol-gel method. Perturbed gamma–gamma angular correlation (PAC) spectroscopy using 111 In– 111 Cd probe nuclei was employed for these measurements. A methodology was developed for sample preparation that were prepared by sol-gel method from pure metallic Sn (99.9999%) and Co (99.9998%) as starting materials. Carrier-free 111 In was added to the precursor sol-gel solution prior to the formation of gel. PAC measurements were carried out to follow the formation of the SnO 2 . PAC measurements were carried out in the temperature range from 10 k to 1123 K and the results show that the electric quadrupole frequency depends on the annealing temperature. Keywords SnO 2 · PAC spectroscopy · Electric-field gradient 1 Introduction The search for diluted magnetic semiconductors with ferromagnetic ordering at room temperature has attracted a great deal of interest in recent years. Several wide band- gap semiconductor oxides such as ZnO, TiO 2 , and SnO 2 have been doped with transition metals in an attempt to create magnetic properties without significantly affecting the physical properties of the host [1]. Among these materials, SnO 2 is a good candidate to successfully exhibit intrinsic magnetic ordering when doped with transition a metal due to the n-type conduction and the presence of native oxygen vacancies in this compound as such vacancies seem to play an important role in the ferromagnetic order of semiconductor oxides [2–4]. In the present work, electric quadrupole interactions in pure and Co doped SnO 2 nanocrystalline samples J. M. Ramos (B ) · A. W. Carbonari · M. S. Costa · R. N. Saxena Instituto de Pesquisas Energéticas e Nucleares, IPEN-CNEN/SP, São Paulo, SP, Brazil e-mail: emrjmr@superig.com.br