Dielectric characterization of the phase transitions in Pb1-y/2(Zr1-xTix)(1-y)NbyO3(0.03<=x<=0.04, 0.02<=y<=0.05)

The Curie temperature and the ideal thermal hysteresis of Pb1-y/2(Zr1-xTix)(1-y)NbyO3 (0.03 less than or equal to x less than or equal to 0.04, 0.02 less than or equal to y less than or equal to 0.05) ferroelectric ceramics have been investigated as a function of composition at the F-RH-P-C phase transition. Experimental results are analyzed using the generalized effective field approach and taking into account the composition dependence of the dimensionless parameters g and h corresponding to the second and third terms in the generalized effective held expansion. With this approach we can describe reasonably well the composition dependence of T-C(x,y) at the F-RH-P-C transition and thermal hysteresis Delta T(x,y) in the narrow range of compositions investigated. The effects of the oxygen octahedra tilt in the dielectric constant at the F-RL-F-RH transition have also been investigated as a function of composition. (C) 1997 American Institute of Physics.