Journal of Magnetism and Magnetic Materials 320 (2008) e504–e506 Magnetic properties of polycrystalline Pr x Y 1x Ba 2 Cu 3 O 7d C. Stari a,b , V.A.G. Rivera a , A.J.C. Lanfredi c , C.A. Cardoso a , E.R. Leite c , A.W. Mombru´ d , F.M. Araujo-Moreira a,Ã a Grupo de Materiais e Dispositivos-GMD, Departamento de Fı´sica-UFSCar, Caixa Postal 676, Sa˜o Carlos, Brazil b Instituto de Fı´sica, Facultad de Ingenierı´a, UdelaR, Julio Herrera y Reissig 565, C.C. 30, 11000 Montevideo, Uruguay c LIEC, Departamento de Quı´mica, Centro Multidisciplinar para o Desenvolvimento deMateriais Ceraˆmicos, UFSCar, Caixa Postal 676, Sa˜o Carlos, SP, Brazil d Laboratorio de Cristalografı´a, Estado So´lido y Materiales, DETEMA, Facultad de Quı´mica, UdelaR, Gral. Flores 2124, 11800 Montevideo, Uruguay Available online 23 February 2008 Abstract In this work, we report a part of a systematic study of the influence of the synthesis routes on the properties of polycrystalline samples of Pr x Y 1x Ba 2 Cu 3 O 7d . We have prepared high-quality samples of this material by following a sol–gel method, associated with heat treatment in both an inert argon and an oxygen atmospheres in order to compare their influence on the formation of the superconducting phase. Magnetic measurement (AC susceptibility) show that the superconducting transition temperature (T C ) increases in samples prepared in argon when compared to those prepared in oxygen, for the same composition and Pr fraction less than 0.5. In addition to this, preliminary results of AC and DC magnetic susceptibility show superconductivity for samples with Pr fraction higher than 0.5 (and up to 0.9) prepared under argon flux, which may indicate the existence of stable superconductivity for all compositions, including pure Pr-123. r 2008 Published by Elsevier B.V. PACS: 74.25.Ha; 74.62.c; 74.62.Bf; 74.62.Dh Keywords: Superconductivity; PrBaCuO 1. Introduction The existence or not of superconductivity in samples of PrBa 2 Cu 3 O 7d (Pr-123) is still a polemic subject and an open question. Since the discovery of high temperature superconductivity on YBa 2 Cu 3 O 7d (Y-123), there has been a great interest in substituting different elements for atoms on different sites of Y-123. Generally, the substitu- tion of rare earth elements on the Y-site does not show important effects on the magnetic and superconducting properties. One exception to this behavior is the substitu- tion of Y for Pr. Its partial substitution in a compound of the form Pr x Y 1x Ba 2 Cu 3 O 7d quenches the superconduc- tivity for a certain value of x. However, the mechanism responsible for this suppression is not understood yet existing a great controversy respect of the mechanisms responsible for this behavior in the Pr x Y 1x Ba 2 Cu 3 O 7d system. However, in the last decade, superconductivity in Pr-123 samples has been reported for some authors where the method of syntheses appears to be responsible for the formation of the superconducting phase [1–3]. In this work, we present a systematic study about how the internal atmosphere during the synthesis is influencing the formation of the pure phase and modifying the superconductor transition in the polycrystalline samples of Pr x Y 1x Ba 2 Cu 3 O 7d (0oxo1). 2. Experimental details Bulk polycrystalline samples were prepared by following a chemical route based in a modified polymeric precursor method, also know as Pechini method [4]. This method is recognized to produce very homogeneous samples reducing the presence of secondary phases, in comparison with the traditional method of solid-state reaction [5]. The details of ARTICLE IN PRESS www.elsevier.com/locate/jmmm 0304-8853/$ - see front matter r 2008 Published by Elsevier B.V. doi:10.1016/j.jmmm.2008.02.096 Ã Corresponding author. Tel.: +55 16 3351 8224; fax: +55 16 3361 4835. E-mail address: faraujo@df.ufscar.br (F.M. Araujo-Moreira).