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

The microscopic mechanisms of the negative electrocaloric effect (ECE) of the single-phase (1-x)(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 (Delta T) to only negative values. The origin of the uniform negative ECE of BNT-BT-BST is discussed. (C) 2013 AIP Publishing LLC.