Interpretation of the Electrocaloric Effect in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 Solid Solutions

Results of direct measurements of electrocaloric effect and polarization are mutually compared in solid solutions 0.4Na(1/2)Bi(1/2)TiO(3)-(0.6-x)SrTiO3-xPbTiO(3). Three temperature regions are distinguished in respect of a phase transition temperature. Above the phase transition, electrocaloric effect is determined by orientation of polar nanoregions by electric field. In wide temperature regions above and below the phase transition temperature, the difference between results, obtained from direct electrocaloric effect measurements and from polarization hysteresis loops, is explained by temperature dependence of concentration of polar nanoregions, oriented by electric field. Existence of a common T(P) curve for all temperatures in the ferroelectric state indicates that polarization can be treated as a parameter, which solely determines electrocaloric effect in this state.