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Ba 1-y-x Pr 2y/3 ⃞ y/3 (Na 0.5 Bi 0.5) x Ti 0.9 Zr 0.1 O 3 (y = 0.005; x = 0.05, 0.1 and 0.15) (BZT-Pr-xNBT) ceramics were prepared using a solid state reaction method. X-ray diffraction (XRD) analysis at room temperature (RT) showed a tetragonal perovskite structure for all compositions. By adding Na 0.5 Bi 0.5 TiO 3 (NBT) on BZT-Pr ceramic, a core-shell grain structure is developed, responsible for an improved dielectric temperature stability with broadened curves at the lower dielectric peak (T l) and the Curie temperature (T C). The temperature coefficient of capacitance curve of the composition BZT-Pr-0.15NBT satisfied the EIA X7R specification and the T C value is successfully increased. These compositions are of relaxor type at T l , which was found near RT. All Raman bands show a broadening with the increasing of NBT content. The remanent polarization (P r), the coercive field (E C) and the piezoelectric coefficient (d 33) decrease when the NBT content increases. The photoluminescence (PL) results exhibit a strong red emission (at 617 nm and 649 nm) for all ceramics. • Ba 1-y-x Pr 2y/3 q y/3 (Na 0.5 Bi 0.5) x Ti 0.9 Zr 0.1 O 3 (y=0.005; x=0.05, 0.1 and 0.15) ceramics were prepared. • The dielectric temperature stability was improved. • The composition BZT-Pr-0.15NBT satisfied the EIA X7R specification. • All compositions are of relaxor type near RT. [ABSTRACT FROM AUTHOR]

• The BST ceramic was prepared by solid state reaction. • Temperature dependence dielectric study showed relaxor kind phase transition. • Modified Debye theory has been adopted to describe the phenomenon of relaxation. • The maximum energy-storage efficiency is 41% for BST ceramic. • The pyroelectric energy harvesting property was studied in BST ceramic. Ferroelectric materials are used in a number of applications such as sensors, transducers and health monitoring systems. The multi-physical coupling ability possessed by these materials has been established to be useful for energy harvesting applications. Lead-free BaTi 0.91 Sn 0.09 O 3 ceramic has been successfully synthesized by the conventional solid-state method. The structural information of our sample has been determined by combining the Rietveld refinement using X-ray diffraction data and the Raman spectra. Based on the dielectric properties, the ferroelectric behavior of relaxor has been observed. Permittivity data have been fitted based on empirical laws describing the diffuse phase transition in the relaxor. A saturated hysteresis loop has been obtained at room temperature. The variation of remnant polarization, maximum polarization and squareness of the hysteresis loop as a function of temperature are in good accordance with phase transition deduced from dielectric properties. Based on Arrhenius' law, the link between the temperature and the back-switching polarization is estimated in order to assess the average activation energy. Our sample has shown a recovered energy density equal to 48.18 mJ/cm3 at 110 °C under an electric field of 30 kV/cm, with an energy efficiency of 41%. Furthermore, the properties of pyroelectric energy harvesting according to Olsen cycle have been studied. The maximum density of pyroelectric energy harvesting per cycle for our studied ceramic has been calculated. It was found to be 210 kJ/m3 for an electric field of 0–30 kV/cm and in temperature ranging from 20° to 120°C. This result leads to the ability to use our sample for energy conversion applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the results of the electrical conductivity measurements for KCaH3−x F x series with (x =1, 1.5, 2, 2.5) in the temperature range 298–503K. The activation energy of the electrical conductivity for the studied compounds depends on hydrogen amount and Reau''s criteria. Differential thermal analysis curves were measured in the same temperature range 298–503K. Possible correspondence between preferential order given by X-ray diffraction, thermal behaviour and electrical properties are discussed. [Copyright &y& Elsevier]

The effect of Pr 3+ addition on structural, electrical, and optical properties of Ba 1− x Pr 2 x /3 Ti 0.925 (Yb 0.5 Nb 0.5 ) 0.075 O 3 (0.3% ≤ x ≤ 1%) ceramics was investigated. X-ray studies have allowed the identification of a continuous solid solution with P 4mm-tetragonal symmetry of all prepared samples. Incorporation of Pr 3+ was found to improve ferroelectric and piezoelectric properties with an optimum at the critical concentration of 0.005. Photoluminescence properties revealed that the introduction of Pr 3+ ions gives rise to the green and red photoemissions and permitted to shed more light on the created structural disorder and shallow defects. This effect was confirmed by Raman spectroscopy investigation. The presence of Pr element in such materials may have significant technological promise in novel multifunctional devices. [ABSTRACT FROM AUTHOR]