aDepartment of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, People’s Republic of China Received 14 February 2007; revised 29 April 2007; accepted 2 May 2007. by F. De la Cruz. Available online 8 May 2007.
Abstract
We have synthesized NaxAy(H3O)zCoO2wH2O (A=Mg, Ca, Sr and Ba) superconductors via ion exchange at ambient conditions. The extent of incorporation of alkaline-earth elements was found to be related to the similarity in size between the guest ion and the host one. In the case of A=Ca, about half of the sodium was successfully replaced by calcium. All the synthesized samples were shown to be superconducting with the Tc from 3.1 to 4.5 K.
Keywords: A. Superconductors; B. Chemical synthesis
wH2O (A=Mg, Ca, Sr and Ba) superconductors via ion exchange 
