High-Pressure X-Ray Study on (L1-xAx)aCubOcSystem

The (L 1-x A x ) a Cu b O c system have high T c superconductivity, where L stands for La, Y and so on, A for the alkaline earth elements, like Ba, Sr and so on. The pressure effect on the lattice constants of YBa 2 Cu 3 O 7-y has been measured at room temperature up to 60 kbar. Compression coefficients of a- and c-axis are found to be almost the same value of (3.3±0.3)×10 -4 kbar -1 , which is larger than the value for (La 0.9 Sr 0.1 ) 2 CuO 4 and the ratio of c/a is found to be almost constant, whose tendency was observed in (La 0.9 Sr 0.1 ) 2 CuO 4 . But the ratio of a/b decreases slightly under pressure.