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The present paper reports the effect of Yttrium substitution on the structural, microstructure, dielectric, ferroelectric, and electrocaloric (EC) properties of the lead-free (Na0.5 Bi0.5)0.94 Ba0.06TiO3 (abbreviated as NBT-6BT) ceramics. For a small quantity of Yttrium (x = 0.01 and 0.05), the X-ray diffraction and Raman spectra exhibit the coexistence of rhombohedral and tetragonal phases at room temperature. However, with x = 0.08 composition, a structural change to pseudo-cubic phase was identified. By adding a small amount of Yttrium, the ferroelectric properties were improved by increasing the remnant polarization from (Pr = 27µC/cm2) for x = 0 up to (Pr = 36µC/cm2) for x = 0.01. This resulted in an improvement of 30% in the estimated ferroelectric parameters as well as an improvement in the piezoelectric properties, as measured by the value of d33 of 130 pC/N. The electrocaloric temperature change (ΔT) is calculated by a direct method using Differential Scanning Calorimetry (DSC) to be at more than 1 K at 5 kV/mm for x = 0.01. Despite the minimal amount employed, our observations lead us to say that the introduction of Yttrium into the NBT-6BT ceramic has directly affected the properties of this material. Nevertheless, with a higher content of Yttrium (x = 0.08), a sudden decrease of both ferroelectric and EC effect was observed. The declined properties at higher contents may originate from the structural change which can influence the polar distribution in the structure. [ABSTRACT FROM AUTHOR]

On the basis of comparative study of the morphology of silver nanoparticles deposited on a surface of single crystalline NH2(CH3)2Al(SO4)2 × 6H2O (DMAAlS) and glass as well as of the absorption spectra of these composites the impact of the ferroelectric phase transition of the "order–disorder" type on the surface plasmon resonance (SPR) was investigated.The observed anomalies of the SPR band parameters were explained in terms of the resonance type coupling between the dipole clusters arising in a narrow region in vicinity of the Curie point and the free electrons within the silver nanoparticles. It was shown that such a coupling is followed by decreasing of these particles' polarizability under the influence of a high frequency electric field of the propagating light photons. The mechanism of growth of the peculiar type of the silver nanoelements on the surface of DMAAlS single crystals—so-called nanowells—is proposed. [ABSTRACT FROM AUTHOR]

The present work reports anomalous ferroelectric properties of two nanocomposites containing oxidized multiwalled carbon nanotubes (ox-MWCNT) as an electrically conductive filler combined with each of hydrogen-bonded ferroelectrics of potassium dihydrogen phosphate (KDP) and triglycine sulfate (TGS). It was shown that the influence of ox-MWCNT led to the anomalous increase in a phase transition point, domain-wall freezing temperatures and coercive fields in ferroelectric parts of the composites. The OH radicals equipped on the carbon nanotube surface after oxidation were responsible for the observed anomalies. [ABSTRACT FROM AUTHOR]

Studies of preliminary structural and detailed frequency–temperature dependence of electrical (dielectric, impedance, polarization, and conductivity) properties of Bi/Na-modified barium titanate compound have been performed in this work. The proposed compound has been synthesized by a conventional solid-state sintering route with a composition of (Ba0.8Bi0.1Na0.1)TiO3. The prepared sample has been pre-heated (calcined) at 1050 °C. Preliminary structural analysis using X-ray diffraction method of the calcined powder confirms the phase purity of the prepared barium titanate compound with tetragonal symmetry. The pellet of this compound has been sintered at 1100 °C. Study of the surface morphology of the pellet by scanning electron microscope (SEM) reveals the homogeneous distribution of grains throughout the sample surface. The dielectric study in the temperature range of 25–500 °C at different frequencies (1 kHz to 1 MHz) shows a high dielectric constant and low tangent loss in a wide temperature range. The temperature response of AC conductivity with impedance spectrum confirms the semiconducting nature of the material at high temperatures. The Nyquist plots reflect the grain and grain boundary contributions to the conduction mechanism of this modified BaTiO3 compound. The existence of ferroelectricity at room temperature of the above sample is confirmed by polarization versus electric field (P–E hysteresis loop) measurements. The J versus E characteristic suggests the Ohmic conduction mechanism of the Bi/Na-modified barium titanate compound. All the studied properties conclude that this composition has potential for device application in the electronic industry. [ABSTRACT FROM AUTHOR]