Satyendra Singh

Giant electrocaloric and energy storage performance of [(K 0.5 Na 0.5 )NbO 3 ] (1−x) -[LiSbO 3 ] x nanocrystalline ceramics

Electrocaloric (EC) refrigeration, an EC effect based technology has been accepted as an auspicious way in the development of next generation refrigeration due to high efficiency and compact size. Here, we report the results of our experimental investigations on electrocaloric response and electrical energy storage properties in lead-free nanocrystalline (1u2009−u2009x)K0.5Na0.5NbO3-xLiSbO3 (KNN-xLS) ceramics in the range of 0.015u2009≤u2009xu2009≤u20090.06 by the indirect EC measurements. Doping of LiSbO3 has lowered both the transitions (TC and TO–T) of KNN to the room temperature side effectively. A maximal value of EC temperature change, ΔTu2009=u20093.33u2009K was obtained for the composition with xu2009=u20090.03 at 345u2009K under an external electric field of 40u2009kV/cm. The higher value of EC responsivity, ζu2009=u20098.32u2009×u200910−7u2009K.m/V is found with COP of 8.14 and recoverable energy storage of 0.128u2009J/cm3 with 46% efficiency for the composition of xu2009=u20090.03. Our investigations show that this material is a very promising candidate for electrocaloric refrigeration and energy storage near room temperature.

Presence of a monoclinic (Cc) phase in the (1−x)BiFeO3-xCaTiO3 solid solution nanoparticles: A Rietveld study

We present here the results of structural investigations on magnetoelectric multiferroic (1u2009−u2009x)BiFeO3-xCaTiO3 (BF-xCT) solid solution nanoparticles, synthesized by the sol–gel method, using Rietveld analysis on powder x-ray diffraction data in the compositional range of 0 ≤u2009xu2009≤u20090.60. The stability of various crystallographic phases in BF-xCT solid solution nanoparticles at room temperature is determined accurately. The structure of BF-xCT solid solution nanoparticles is monoclinic (Cc) for 0.10 ≤u2009x ≤u20090.22 and orthorhombic (Pbnm) for x ≥u20090.28, whereas the two phases coexist in the morphotropic phase boundary region of 0.23 ≤u2009x ≤u20090.27 as confirmed by Rietveld analysis. We have established the phase diagram at room temperature for BF-xCT solid solution nanoparticles as a function of composition. Transmission electron microscopy confirmed the morphology, microstructure, and the crystallinity of the nanoparticles, and the average particle size is found to be in the range of 30–50u2009nm.