A novel sol–gel route to synthesize (Sr0.5Ba0.5)Nb₂O₆ ceramics with enhanced electrocaloric effect

Abstract

(Sr 0:5 Ba 0:5 )Nb 2 O 6 ultra-fine powders were synthesized by a novel sol-gel route, and the mechanism of the reaction was discussed. SrCO 3 , BaCO 3 , oxalate niobium and citric acid were used to initiate the sol-gel process, and ethylene glycol (EG) was added to further polymerize the cross-linking structure. The evolution of the (Sr 0:5 Ba 0:5 )Nb 2 O 6 phase, the reaction process and the microstructures were investigated by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy, DSC-TG and scanning electron microscopy. The synthesis temperature of the (Sr 0:5 Ba 0:5 )Nb 2 O 6 powders reached as low as 1200 C, and the size and morphology of the powders were controlled by temperature. By adjusting the calcination temperature, we obtained (Sr 0:5 Ba 0:5 )Nb 2 O 6 powders with uniform sizes of 20 nm to 500 nm. Then, dense (Sr 0:5 Ba 0:5 )Nb 2 O 6 ceramics were successfully prepared using these ultrafine powders. Finally, an enhanced electrocaloric effect (ECE) value of 0.35 C was obtained at 100 kV/cm.

Investigations of nano-crystalline Sr0.5Ba0.5Nb2O6 and bulk ceramics synthesized by a polymerization method using PEG400

“…The formation of Sr 0.5 Ba 0.5 Nb 2 O 6 together with an amorphous fraction at low temperature can often be seen using wet-chemical methods [21,30,32,39]. Recently, Chen et al [19] prepared Sr 0.5 Ba 0.5 Nb 2 O 6 by a sol-gel synthesis using 1,2-ethanediol and citric acid as polymerization agents. Calcination of that gel resulted in considerable amounts of secondary phases up to 1100 °C.…”

Twin‐Peak Electrocaloric Effect in Ferroelectric Phase of Diffusive SrBi1.98La0.02Nb2−xTaxO9 Materials

“…[2,3] Aurivillius phases with relaxor-like diffused behavior are popular for medium and large-scale refrigeration. [4] Quian et al and Goupil et al reported the ECE enhancement near the critical point, morphotropic phase boundary, respectively, in bulk ceramics due to the presence of a mix of polar phases of nanoregions with different symmetries. [5,6] Large entropic changes occur near phase transitions like ferroelectric to paraelectric, antiferroelectric to ferroelectric, and even in ferroelectric to ferroelectric; compositional modifications are known crucial to the nature of phase transition.…”

“…Moreover, operating temperature range T span (the range of temperature over which ΔT stays 0.9 times ΔT peak ) for achieving maximum ECE change at comparatively low electric fields is also desirable. [4,5] Recently published work by Chen et al and Hamad in an isolated manner on strontium bismuth niobate (SBN) bulk and thin films reiterated the inclination of researchers to stimulate ECE in Sr-based bismuth-layer structured ferroelectrics (BLSF) family members for augmented solid-state refrigeration. [4,9] An assisting study by Axelsson et al on the effects of relaxor characteristics and diffused phase transition on ECE strength in strontium bismuth niobate tantalate (SBNT) compounds proved to be very useful.…”

“…[4,5] Recently published work by Chen et al and Hamad in an isolated manner on strontium bismuth niobate (SBN) bulk and thin films reiterated the inclination of researchers to stimulate ECE in Sr-based bismuth-layer structured ferroelectrics (BLSF) family members for augmented solid-state refrigeration. [4,9] An assisting study by Axelsson et al on the effects of relaxor characteristics and diffused phase transition on ECE strength in strontium bismuth niobate tantalate (SBNT) compounds proved to be very useful. [10] On the basis of well-supported foundations laid by mentioned reports, [1][2][3][4][5][6][7][8][9][10] this work targets to critically investigate the mutual correlation among diffused phase transition and electrocaloric response in SrBi 1.98 La 0.02 Nb 2-x Ta x O 9 (SBLNT) materials.…”

“…[4,9] An assisting study by Axelsson et al on the effects of relaxor characteristics and diffused phase transition on ECE strength in strontium bismuth niobate tantalate (SBNT) compounds proved to be very useful. [10] On the basis of well-supported foundations laid by mentioned reports, [1][2][3][4][5][6][7][8][9][10] this work targets to critically investigate the mutual correlation among diffused phase transition and electrocaloric response in SrBi 1.98 La 0.02 Nb 2-x Ta x O 9 (SBLNT) materials. Selective SBLNT compounds were prepared by introducing tantalum on B-site keeping lanthanum-induced rigid bismuth oxide layer which implicated low porosity, growth of orthorhombic structure, and gradually decreasing phase transition values 683 K, 663 K, 568 K, respectively, for SBLNT (x ¼ 0.5), SBLNT (x ¼ 1.0), SBLNT (x ¼ 1.5) along with rise in diffusivity.…”