BRIEF COMMUNICATION Synthesis of monoclinic KGd(WO 4 ) 2 nanocrystals by two preparation methods M. Galceran Æ M. C. Pujol Æ C. Me ´ndez Æ A. Garcı ´a Æ P. Moreno Æ L. Roso Æ M. Aguilo ´ Æ F. Dı ´az Received: 1 February 2007 / Accepted: 6 February 2008 / Published online: 12 March 2008 Ó Springer Science+Business Media B.V. 2008 Abstract The monoclinic crystalline phase of KGd(WO 4 ) 2 is a well-known solid-state laser host. The present article describes how monoclinic nano- crystals of KGd(WO 4 ) 2 are synthesized by two different methodologies: the sol–gel modified Pechini method and femtosecond pulsed laser ablation of bulk material in deionized water. Transmission Electron Microscopy images show KGdW nanocrystals between 15 and 100 nm for both methods. The nanocrystals are studied by X-ray powder diffraction (XRD) in order to identify the crystalline phase and to refine the unit cell parameters. For the sol–gel modified Pechini method, differential thermal analy- ses and XRD techniques were also used to optimize the method of preparation. Keywords Nanostructures Á Optical materials Á Sol–gel chemistry Á X-ray diffraction Á Crystal structure Á Laser ablation Introduction The monoclinic double tungstates KRE(WO 4 ) 2 (RE = Gd, Y and Lu) are a well-known laser host materials; their high crystallographic anisotropy and high non-linear third-order coefficient are particularly interesting features (Kaminskii 2003). Moreover, the high absorption and emission cross section values with rare-earth doping mean that for some laser applications, these materials can be a real alternative to the widely used YAG (Griebner et al. 2005; Mateos et al. 2006, 2004; Batay et al. 2002; Kaminskii et al. 1992). Recently, YAG and sesquioxides RE 2 O 3 ceramic lasers have been described as interesting alternatives to single crystal laser materials (Kamin- skii 2003). Preparing nanoparticles from both families of compounds is the first step to achieving a ceramic host with a highly efficient laser performance. In this article, we present two methodologies for obtaining nanoparticles of the monoclinic double tungstates, from which laser ceramics can be made. To date, no KGd(WO 4 ) 2 (hereafter KGdW) nanopar- ticles have been synthesized. The Pechini sol–gel method was published in 1967 (Pechini 1967). At present, the literature uses this method to prepare M. Galceran Á M. C. Pujol (&) Á M. Aguilo ´ Á F. Dı ´az Fı ´sica i CristalÁlografia de Materials (FiCMA), Universitat Rovira i Virgili, Campus Sescelades. c/ MarcelÁlı ´ Domingo, s/n, 43007 Tarragona, Spain e-mail: mariacinta.pujol@urv.cat C. Me ´ndez Á A. Garcı ´a Á P. Moreno Á L. Roso Servicio La ´ser, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca, Spain P. Moreno Departamento de Ingenierı ´a Meca ´nica, Universidad de Salamanca, Avenida Fernando Ballesteros s/n, 37700 Bejar, Salamanca, Spain 123 J Nanopart Res (2009) 11:717–724 DOI 10.1007/s11051-008-9375-2