Influence of thermal conditions on the electrocaloric effect in a multilayer capacitor based on doped BaTiO_(3)

We present the results of studies of thermal expansion,heat capacity,permittivity,polarization and the influence of different thermal conditions on the intensive electrocaloric ffect(ECE),△T_(AD),in a commercial multilayer capacitor based on doped BaTiO_(3).Investigations in a wide temperature range revealed one anomaly in the behavior of the physical properties at about 290 K characteristic for the relaxors.Direct measurements showed a high reversibility of ECE under equilibrium thermal conditions.Good agreement was found between the values of△T_(AD) determined by direct and indirect measurements at the electric field up to 15.4 kV/cm.Quasi-isothermal conditions lead,firstly,to decrease of large△T_(AD)≈0.94 K obtained in adiabatic conditions under E=308 kV/cm to 0.87 K,and,secondly,the appearance of a difference between the values of △T^(ON) and△T^(OFF) determined when the electric field is applied and removed.Using this phenomenon and changing the frequency of the periodic electric field,E=15.4 kV/cm,the efect of cooling was obtained equal to[(OT^(ON)+AT^(OFF))/2]_(max)=-0.032 K.The results obtained are useful for further development of the electrocaloric refrigeration technique without thermal switches.