Solid State Sciences 5 (2003) 1369–1376 www.elsevier.com/locate/ssscie Characterization of cubic ceria–zirconia powders by X-ray diffraction and vibrational and electronic spectroscopy Vicente Sánchez Escribano a,∗ , Enrique Fernández López a , Marta Panizza b , Carlo Resini b,c , José Manuel Gallardo Amores d , Guido Busca b,c a Departamento de Química Inorgánica, Facultad de Ciencias Químicas, P a . de la Merced s/n, 37008 Salamanca, Spain b Dipartimento di Ingegneria Chimica e di Processo, Università di Genova, P.le J.F. Kennedy, 16129 Genova, Italy c INFM, c/o Dipartimento di Fisica, Università di Genova Via Dodecaneso 33, 16146 Genova, Italy d Laboratorio Complutense de Altas Presiones, Dpto. Química Inorgánica I, F a Química, U. Complutense, 28040-Ciudad Universitaria, Madrid, Spain Received 18 March 2003; received in revised form 13 July 2003; accepted 25 July 2003 Abstract The X-ray diffraction (XRD) patterns and the Infrared, Raman and UV–visible spectra of CeO 2 –ZrO 2 powders prepared by co-precipitation are presented. Raman spectra provide evidence for the largely predominant cubic structure of the powders with CeO 2 molar composition higher than 25%. Also skeletal IR spectra allow to distinguish cubic from tetragonal phases which are instead not easily distinguished on the basis of the XRD patterns. All mixed oxides including pure ceria are strong UV absorbers although also absorb in the violet visible region. By carefully selecting their composition and treatment temperature, the onset of the radiation that they cut off can be chosen in the 425–475 nm interval. Although they are likely metastable, the cubic phases are still pure even after heating at 1173 K for 4 h.  2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. 1. Introduction The oxides of tetravalent transition elements constitute relevant products for the inorganic chemical industry and object of research in relation to several applications. They are at least partially mutually soluble and present also inter- esting properties from the point of view of their solid state chemistry. Zirconia is found in nature in small quantities as the mineral Baddeleyite (monoclinic zirconia) and can also exist as tetragonal and cubic fluorite-like polymorphs, both stable at higher temperature but stabilized by doping down to room temperature [1]. Cerium dioxide only presents a cu- bic fluorite-type polymorph. However, it loses oxygen easily becoming largely nonstoichiometric and giving rise to sev- eral suboxides up to the sesquioxide Ce 2 O 3 [2]. Due to the common fluorite-like structure, they are able to form solid solution phases in a broad compositional range [3]. Zirconia ceramics are utilized as refractory materials in furnace construction, in the manufacture of melting cru- cibles, and in the steel industry for continuous casting noz- * Corresponding author. E-mail address: vsescrib@usal.es (V. Sánchez Escribano). zles [1,4]. Due to the total transparency to the visible light and the high index of refraction (2.1–2.2), zirconia is a good white pigment, and a good opacifier [5]. Ce oxide based ce- ramics present different applications, i.e., in the fields of ce- ramic superconductors [6,7], gas sensors [8] and catalytic materials [9]. Of particular interest are also the applications of the optical properties of ceria-based materials for the pro- duction of thin film optical devices [10,11] and as a UV- blocking agent for cosmetics [12]. In the last several years, ceria–zirconia mixed oxides have attracted a great deal of attention in catalysis, because they combine the highly re- fractory properties of zirconia with the oxygen-storage prop- erties of ceria [13]. They are also promising materials for Solid Oxide Fuel Cell Technology [14]. These materials show good thermal resistance [15,16] as well as enhanced redox properties. It is evident that their yields for the above mentioned applications depend critically on their electronic properties. Deep investigations on the vibrational and elec- tronic spectra of pure zirconia have been performed [17–19]. Additionally, detailed studies have been reported on the sur- face properties of ceria–zirconia [20,21]. To our knowledge, less attention has been paid yet to investigate the bulk spec- troscopic properties of the Ce–Zr mixed oxides. We report here a study on the spectroscopic properties of which deals 1293-2558/$ – see front matter  2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2003.07.001