Bulk samples of Yb1-xDyxBa2Cu3O7-y composition, where (x = 0, 0.25, 0.
5, 0.75 and 1.0) are prepared and studied with respect to formation of
superconducting 123 orthorhombic phase. It is found that the orthorho
mbicity as well as superconducting transition temperature (T-co) incre
ase almost linearly with the Dy concentration. Samples with x = 0 and
x = 1 have T-co = 87.6 K and 90.2 K, respectively.