AC suscptibility study of YBCO sintered samples near the transition temperature

Y1Ba2Cu307_x sintered samples have been investigated near the transition temperature by means of AC susceptibility technique. In particular, the intragranular contribution to the imaginary part of susceptibility (Z") has been studied as a function of the field frequency (f = 17 Hz + 1070 Hz) in a narrow temperature range (few degrees) around T c (= 92.0 K). Different frequency dependences of Z" have been found as the temperature varies. For temperatures T<91.9 K Z" is found to increase linearly with In f, whereas for T~_ 91.9 K a linear frequency dependence is found. Moreover, for T<92.3K the zero frequency limit approaches to a finite value, whereas for T>92.3K such limit is zero.