Superconductivity in Alkaline Earth-Substituted La2CuO4-y

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Science  03 Apr 1987:
Vol. 236, Issue 4797, pp. 73-75
DOI: 10.1126/science.236.4797.73


La2CuO4-y ceramics containing a few percent of Ca2+, Sr2+, and Ba2+ ions have been prepared. Resistivity and susceptibility measurements exhibit superconductive onsets (as in earlier Ba2+-containing samples). The onset temperature La2CuO4-y with Sr2+ is higher and its superconductivity-induced diamagnetism larger than that found with Ba2+ and Ca2+. This is proof that the electronic change resulting from alkaline earthdoping, rather than the size effect, is responsible for superconductivity. The ionic radius of Sr2+ is close to that of La3+ for which it presumably substitutes.