Phase transitions in Pb(Yb1/2Nb1/2)O-3-PbTiO3 solid solutions

High-resolution heat capacity measurements of (1 - x)Pb(Yb1/2Nb1/2)O3-xPbTi O3 with x = 0, 0.02, 0.04, 0.06, 0.08 were carried out in the temperature r ange from 80 K to 590 K using a modified adiabatic calorimeter. The dielect ric constant was also obtained for x = 0 and 0.02 samples between 300 K and 600 K at the measuring frequency of 10 kHz. The beat capacity data clearly reveal that the transition is of the first-order nature. The transition te mperature decreases linearly and the heat capacity peak associated with the transition becomes broader as x increases. An anomaly in dielectric consta nt was also observed at the transition temperatures. It is of particular in terest to note that the transition revealed by both heat capacity and diele ctric constant is most abrupt at x = 0.02, not x = 0, and the origin of thi s peculiar behavior seems to lie in the dynamics.