Synthesis, structure, and superconductivity of La Sr K Na CuO.

Sodium and potassium have been doped into LaSrCuO to form La Sr K Na CuO solid solutions by a solid-state reaction, which crystallizes in the 4/ space group when 0 ≤ < 0.16 and when 0.16 < ≤ 0.25. With the equivalent replacement of four Sr by one Na, one K and two La, it is very interesting to find that (the definition is presented in the introduction part) of La Sr K Na CuO does not remain constant with an increase in but first increases from 14.8 K for = 0.00 to 33.9 K for = 0.10 and then decreases to 18.5 K for = 0.175.