The influence of Rb2CO3 additive on the properties of YBCO was investi
gated. The impurity was added to the usual stoichiometry of Y1Ba2Cu3Oy
to produce an initial batch with general formula Y1Ba2Cu3(Rb)xOy wher
e x=0 to 0.60. Only traces of (2.21 x 10(-2) wt. %) Rb were found in a
ll samples after final baking. Adding Rb shifted the temperature T(on)
of the ''magnetic transition'' towards lower temperatures without aff
ecting the electrical HTSC characteristics and improved the grain size
homogeneity.