An investigation was made of broad phase transitions to the paraelectric state of (1 -x)Pb(Yb1/2Nb1/2)O-3-xPb(Lu1/2Ta1/2)O-3 solid solution for 0.45 less than or equal to x less than or equal to 0.50. The broadening of these transitions was found to depend on the position of the sample in the phase diagram, with the strongest broadening for a composition within the hysteresis range separating the ferroelectric and antiferroelectric states. An interaction mechanism between the ferroelectric and antiferroelectric domains is proposed to explain the broadening of the phase transitions.