Phase diagram of TTB ferroelectric compounds Pb1−xK2xNb2O6
E. Choukri, Y. Gagou, D. Mezzane, M. Elmarssi, Z. Abkhar, M. Elaatmani, I. Luk’yanchuk, P. Saint-Grégoire
Abstract
Substitution of Pb with K in the PbNb2O6 phases leads to a new composition of solid solution with chemical composition Pb1−xK2xNb2O6 with x ranging from 0 to 0.34 in steps of 0.05. Ferroelectric ceramics were synthesized using solid state reaction between the corresponding oxides and carbonates. Powders are pressed and heated into ceramics and their compaction is about 92%. The tetragonal tungsten bronze (TTB) structure at room temperature was confirmed by X-ray diffraction (XRD). The temperature dependence of dielectric permittivity was measured from 35 to 600°C in the 20-106 Hz frequency range.
Transition temperature decreases with the lead concentration while from x=0, with Tc=600°C and to x=0.3 with Tc=388°C. These measurements permit to present a basical phase diagram of this family compound showing the evolution of the characteristic transition temperature Tc versus temperature. The behaviour of Tc is in agreement with theoretical study of the ferroelectric phase transition in TTB using Monte Carlo (MC) simulation. The dielectric properties of these ceramics are similar to those obtained on a single crystal and illustrate the quality of preparative conditions.
Transition temperature decreases with the lead concentration while from x=0, with Tc=600°C and to x=0.3 with Tc=388°C. These measurements permit to present a basical phase diagram of this family compound showing the evolution of the characteristic transition temperature Tc versus temperature. The behaviour of Tc is in agreement with theoretical study of the ferroelectric phase transition in TTB using Monte Carlo (MC) simulation. The dielectric properties of these ceramics are similar to those obtained on a single crystal and illustrate the quality of preparative conditions.