Unification of the negative electrocaloric effect in Bi1/2Na1/2TiO3-BaTiO3 solid solutions by Ba1/2Sr1/2TiO3 doping

Abstract

The microscopic mechanisms of the negative electrocaloric effect (ECE) of the single-phase (1Àx)(0.94Bi 1/2 Na 1/2 TiO 3 -0.06BaTiO 3 )-xBa 1/2 Sr 1/2 TiO 3 (BNT-BT-BST) perovskite solid solutions fabricated via the sol-gel technique are explored in this study. Dielectric and mechanical relaxation analyses are employed to investigate the ferroelectric and structural transitions of the samples. The electrocaloric properties of the samples were measured by thermodynamics Maxwell relations. The difference between the depolarization temperature (T d ) and the maximum dielectric constant temperature (T m ) was found to decrease with increasing BST content. Doping with BST stabilized the ferroelectric phase along with unifying the EC temperature changes (DT) to only negative values. The origin of the uniform negative ECE of BNT-BT-BST is discussed. V C 2013 AIP Publishing LLC. [http://dx

Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

“…Some of the highest ECE performances ever reported were found in the Pb-containing compounds close to their MPB, such as PMN-30PT. 4 The ECE of some lead-free materials with compositions near the CP, such as Zr-doped Ba 0.8 Ca 0.2 TiO 3 , 13 Sn-doped BT, 14 or Sr-doped NBT-BT, 15,16 has also been reported, but very few were studied by direct ECE measurements.…”

Enhanced Electrocaloric Effect in Pre‐stressed Ferroelectric Materials

“…Similar observations have been reported by several other independent groups based on Maxwells relations. [9,[56][57][58] However, all such studies were made for unstressed materials. The maximum ECE reported in the literature for unstressed bulk samples of BNT-based materials is in the vicinity of 1.5-1.75 K. [56,58] Our own prediction for unstressed BNT-BT samples is close to these values, and hence, the accuracy of our approach is reaffirmed.…”

Double hysteresis loops and large negative and positive electrocaloric effects in tetragonal ferroelectrics

“…[25][26][27][28][29][30][31][32][33][34][35][36] Antiferroelectrics (AFEs) are characterized by an antipolar crystal structure with two (or more) spontaneous polarizations of opposite directions in a crystalline lattice and manifest the zero macroscopic spontaneous polarization and the induced antiferroelctric-to-ferroelectric phase transition by high-enough electric field. Although most of EC effects in ferroelectric/antiferroelectric materials were found to be positive in the past decades, an optimized cooling cycle is to utilize both positive and negative EC effects.…”