Dispersive Dielectric Behaviour of Ternary 0.49BiFeO3-0.20Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 (BF-PMN-PT) Ceramic Near Morphotropic Phase Boundary Using a Modified Debye Model.

A near-morphotropic phase boundary (MPB) composition of ternary 0.49BiFeO₃-0.20Pb(Mg_1/3Nb_2/3)O₃-0.31PbTiO₃ (BF-PMN-PT) ceramic was synthesized for various dielectric, ferroelectric and piezoelectric applications using the conventional solid-state reaction method via a two-step columbite precursor technique. Powder x-ray diffraction (XRD) confirms the perovskite phase of the synthesized ceramic with a monoclinic crystal structure belonging to the P1m1 space group. The dielectric properties and the relaxation mechanisms of this ternary ceramic were studied using dielectric spectroscopy measurements for the frequency range of 10 Hz to 1 MHz over a wide range of temperature from 50°C to 400°C. A good dielectric response was observed with a high dielectric constant value (~ 800) that decreases with increasing frequency. A phase transition temperature (T_c = 275°C) and a low dielectric loss were also observed. The dielectric exhibits a clear and distinct Debye-type relaxation in the ferroelectric phase. The measured dielectric data fit quite well with the modified Debye model. Various Debye fitting parameters were obtained which show a temperature-dependent nature. The value of Debye broadening parameter α exhibits a decreasing trend from 0.136 to 0.003 as temperature increases from 50°C to 200°C, after which it increases and attains a maximum value of 0.566 at 350°C. The Cole–Cole plot obtained from the measured data reveals the distributive nature of the sample's dielectric relaxation. [ABSTRACT FROM AUTHOR]