Glass-like behaviour in the relaxor ferroelectric 0.6 Pb(Yb1/2Nb1/2)O-3 0.4 Pb(Lu1/2Ta1/2)O-3

Studies have been conducted on the ferroelectric properties of 0.6 Pb(Y1/2N b1/2)O-3-0.4 Pb(Lu1/2Ta1/2)O-3, a solid solution of the antiferroelectric o xides Pb(Yb1/2Nb1/2)O-3 and Pb(Lu1/2Ta1/2)O-3. X-ray diffraction shows that at room temperature this solid solution has a tetragonal perovskite crysta l structure. Evidence for a diffuse phase transition in this material is pr ovided from measurements of the dielectric and piezoelectric properties and the form of the P-E hysteresis loop. A Frohlich-type model for the relaxat ion time spectrum is shown to model the complex dielectric constant as a fu nction of temperature satisfactorily. Cole-Cole plots of the experimental r eal and imaginary parts of the dielectric constant, epsilon' and epsilon ", as a function of temperature and curves of polarization as a function of t emperature suggest a freezing temperature of 152 K and 173 K respectively, in contrast to Vogel-Fulcher fits of the temperature dependence of the maxi ma in epsilon' and epsilon " which suggest a freezing temperature of 310 K and 308 K respectively. The nature of this diffuse phase transition has bee n interpreted in terms of a glass-like behaviour.