The temperature and magnetic field dependence of the critical current density have been measured for different temperature ranges in YBa2(Cu1-xNix)3O7-y samples. The critical current density near Tc is found to be proportional to (1-T/Tc)3/2 in YBa2Cu3,O7-y. The critical current density is sensitive to external magnetic fields which tends to indicate a possible Josephson granular structure in the samples. A three-dimensional mapping of Jc(H,T) is given.