The Acoustic Internal Friction (IF) of Y_1-xPr_xBa₂Cu₃O_7-δ System

The acoustic internal frction （IF） peaks of Y_1-xPr_xBa₂Cu₃O_7-δ system was studied by the electro-magnetic drive method. Expermental results show that with increasing x of Pr the IF peak around 85K unchanges bassically, but the IF peak around 110K degreases first then disappers in x = 0.7. Combining other experimental data we think that IF peak around 110K is related to electric structure of the system and not directly related to the superconductivity of the samples.