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New compositions of Tetragonal Tungsten Bronze (TTB) ferroelectrics Pb1-xK2xNb5O15(PKN) with x = 0.1, 0.2, 0.25 and 0.3 were synthesized using the solid state reaction method. Structural and electrical properties were examined as a function of the ratio Pb/K using X-ray diffraction, Raman spectroscopy and dielectric measurements. The dielectric permittivity and the loss tangent of each composition have been measured in a frequency range 10 Hz–1 MH and in a temperatures range 25–600°C. It was shown that the Pb substitution induces the diffuse phase transition. [ABSTRACT FROM PUBLISHER]

Abstract: Ferroelectric ceramics Pb2−x K1+x Li x Nb5O15 (PKLN), with , having the tetragonal tungsten bronze (TTB) structure, were synthesized using a solid-state reaction and characterized by X-ray diffraction. The temperature dependence of dielectric permittivity was measured from 35 to 550 °C in the frequency range from 20 Hz to 1 MHz. These measurements permit us to present the phase diagram of this family and the evolution of the transition temperature as function of the chemical composition. [Copyright &y& Elsevier]

Abstract We investigate the lead free ferroelectric perovskite ceramic, (Ba 0.85 Ca 0.15)(Zr 0.1 Ti 0.9)O 3 (BCZT), prepared by sol-gel method. The as-synthesized precursor powder is calcined at 1000 °C for 4 h in order to obtain single-phase perovskite structure. X-ray diffraction (XRD) analysis at room temperature shows the formation of single-phase compound with a tetragonal structure refined in P 4mm space group. The dielectric measurements in a frequency range of [100 Hz-1 MHz] and in a temperature range [35–400 °C] in the ceramic sintered at 1350 °C for 2 h, reveal a high maximum dielectric constant ∼5200 (100 Hz) at 107 °C, which is associated with ferroelectric paraelectric phase transition. The sol-gel method has displayed a very important advantages comparing to the conventional solid-state method. Special emphasis was done to characterize diffuse phase transition (DPT) that occurs close to ∼107 °C. We have shown that the real part of the permittivity close to DPT is well described by Santos–Eiras phenomenological model. Impedance spectroscopy analysis over the frequency range of 100 Hz to 1 MHz illustrated mainly bulk contribution up to 300 °C while grain and grain-boundary effects were present above 300 °C using the impedance spectroscopy technique. Highlights • The XRD study showed a pure perovskite structure without impurities with tetragonal symmetry refined to P4mm space group. • The sol-gel method has displayed a very important advantages comparing to the conventional solid-state method. • The real part of the permittivity close to DPT is well described by Santos–Eiras phenomenological model. [ABSTRACT FROM AUTHOR]