Influence of thermal history on dielectric anomalies in incommensurate (TMA)2ZnCL4

We present new results on tetramethyl ammonium zinc chloride, concerning the role of thermal history of the sample. The influence of a temperature stabilization at various values is described. Relaxation phenomena are found and briefly discussed.     

Improved energy storage and electrocaloric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

Lead-free Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) ceramic powders were synthesized using the sol–gel method. The ceramics thickness was reduced to achieve high-energy storage and large electrocaloric effect in bulk ceramics. Dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for BCZT ceramic with 400 µm. Here, pure crystalline structure and homogenous microstructure were identified by XRD analysis and SEM measurements, respectively. The dielectric measurements revealed a maximum dielectric constant associated with ferroelectric–paraelectric phase transition. The maximum of \(\varepsilon^{\prime}_{{\text{r}}}\) was 17841, around 352 K. Furthermore, the BCZT ceramic exhibited improved energy storage and electrocaloric properties. A high recoverable energy density W_rec of 0.24 J/cm³ and a total energy density W_total of 0.27 J/cm³ with an efficiency coefficient of?~?88% at 423 K under an electric field of 55 kV/cm were obtained. Besides, The maximum value of ΔT?=?2.32 K, the electrocaloric responsivity ζ?=?0.42 K mm/kV, the refrigeration capacity RC?=?4.59 J/kg and the coefficient of performance COP?=?12.38 were achieved around 384 K under 55 kV/cm. The total energy density W_total and the temperature change ΔT were also calculated by exploiting the Landau–Ginzburg–Devonshire (LGD) theory. The theoretical results matched the experimental findings. These results suggest that the synthesized BCZT ceramic with reduced thickness could be a promising candidate for energy storage and electrocaloric applications.

     

Dielectric and Magnetic properties of (1 − x)BiFeO3–xBa0.8Sr0.2TiO3 ceramics

The polycrystalline samples of (1 ? x)BiFeO₃–xBa_0.8Sr_0.2TiO₃ (x = 0, 0.1, 0.2, 0.25, 0.3, 0.4 and x = 1) were prepared by the conventional solid state reaction method. The effect of substitution in BiFeO₃ by Ba_0.8Sr_0.2TiO₃ on the structural, dielectric and magnetic properties was investigated. X-ray diffraction study showed that these compounds crystallized at room temperature in the rhombohedral distorted perovskite structure for x ≤ 0.3 and in cubic one for x = 0.4. As Ba_0.8Sr_0.2TiO₃ content increases, the dielectric permittivity increases. This work suggests also that the Ba_0.8Sr_0.2TiO₃ substitution can enhance the magnetic response at room temperature. A remanent magnetization M_r and a coercive magnetic field H_C of about 0.971 emu/g and 2.616 kOe, respectively were obtained in specimen with composition x = 0.1 at room temperature.     

Chemical Synthesis of Organo-siloxene 2D Materials from Calcium Di-Silicide: Characterization,Dielectric and Electrochemical Studies

Silicon - Silicon is one of the most used materials in semiconductors and electronic devices. Its miniaturization in two-dimensional (2D) scale is now a great challenge to improve and/or extend its...