Role of charge doping and lattice distortions in codoped Mg1-x(AlLi)(x)B-2 compounds

We prepared a series of Mg1-x(AlLi)(x)B-2 samples with 0 <= x <= 0.45 in order to compensate with Li the electron doping induced by Al. Structural characterization by means of neutron and X-ray diffraction confirms that Li enters the MgB2 structure even though in an amount less than nominal one. Experimental evidence points out that Li has almost no effect on the properties of MgB2, being all properties strictly correlated with Al content. In order to further clarify the topic we perform upper critical field measurements on Mg1-x(AlLi)(x)B-2. (c) 2007 Elsevier B.V. All rights reserved.