Abstract
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 (1 − x)K0.5Na0.5NbO3-xLiSbO3 (KNN-xLS) ceramics in the range of 0.015 ≤ x ≤ 0.06 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, ΔT = 3.33 K was obtained for the composition with x = 0.03 at 345 K under an external electric field of 40 kV/cm. The higher value of EC responsivity, ζ = 8.32 × 10−7 K.m/V is found with COP of 8.14 and recoverable energy storage of 0.128 J/cm3 with 46% efficiency for the composition of x = 0.03. Our investigations show that this material is a very promising candidate for electrocaloric refrigeration and energy storage near room temperature.
Highlights
An enormous amount of global energy uses for refrigeration, processing plants and air-conditioners are mainly based on vapor compression technology based on a century ago developed mechanical compressor
The colossal electric fields are the reason for high electrocaloric effect (ECE) in thin films that can be applied till the breakdown field, the cooling effect and specific density are low
The cooling strength of bulk ceramics are of high value but the observed ECE is sufficiently low for practical purposes in commercial refrigeration technologies and the reason behind is the low dielectric strength
Summary
An enormous amount of global energy uses for refrigeration, processing plants and air-conditioners are mainly based on vapor compression technology based on a century ago developed mechanical compressor. There had been a various report on the mentioned materials, but achieved EC temperature change (ΔT) is very less It has been simulated for high polarization change, which is the key factor for ECE; associated with K0.5Na0.5NbO3 (KNN) based ceramics[27] but experimentally there is no report for high positive ECE value so far. It is a ferroelectric material with the perovskite structure which exhibits temperature-dependent spontaneous polarization and possess giant ECE and the best candidate for solid-state cooling[28,29]. We have synthesized lead-free (1-x) K0.5Na0.5NbO3-xLiSbO3 (KNN-xLS) nanocrystalline ceramics with 0.015 ≤ x ≤ 0.06 and obtained the highest ECE value and EC responsivity experimentally by an indirect method based on Maxwell’s approach
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