Sol-Gel Synthesis of the Strontium-Copper Oxycarbonate Superconductor Sr2CuO2(CO3)1−x(BO3)x

Abstract

AbstractWe have developed an ambient-pressure sol-gel synthetic route to superconducting borate-doped Sr2CuO2(CO3) using polyether alkoxide precursors. In our sol-gel preparation, the starting solutions contain strontium and copper alkoxide complexes in 2-(2-methoxy-ethoxy)ethanol. Boron is incorporated into the solution by using an aqueous boric acid solution for hydrolysis. Dried gels were examined by x-ray diffraction and thermal gravimetric analysis. By experimenting with various firing sequences and atmospheres we have established a successful route for reproducibly preparing relatively pure Sr2CuO2CO3 and boron-doped phases. Final products were characterized by x-ray diffraction, elemental analysis and magnetic susceptibility. Samples of nominal composition Sr2CuO2(CO3)0.85(BO2)0.15 are superconducting with a Tc(onset) of ∼25K. Subsequent treatment at 1100°C and 3 GPa for one hour increased Tc(onset) to ∼35K.