Pb(Fe0.5Nb0.5)O-3-BiFeO3-based multicalorics with room-temperature ferroic anomalies

摘要

The search for new single-phase multicaloric materials, combining electrocaloric and magnetocaloric effects, is just at its beginning. Since the highest caloric effects are obtained near ferroic phase transitions, multiferroics with room-temperature ferroic anomalies are promising candidates for multicaloric cooling. In this work, such materials were prepared by tailoring the temperature of the ferroic anomalies by introducing BiFeO3, a material possessing high-temperature ferroic phase transitions, into the multicaloric Pb(Fe0.5Nb0.5)O(3)to form a solid solution. A series of (1-x)Pb(Fe0.5Nb0.5)O-3-xBiFeO(3)(x= 0-0.5) were prepared. Among them, 0.8Pb(Fe0.5Nb0.5)O-3-0.2BiFeO(3)exhibits both dielectric permittivity and magnetic susceptibility anomalies at room temperature and is therefore one of the first such single-phase materials. However, at higher temperatures the material exhibits excessive Joule heating that critically degrades the electrocaloric cooling effect, while the antiferromagnetic nature of the material results in a low magnetocaloric response. Because of that, the multicaloric properties of 0.8Pb(Fe0.5Nb0.5)O-3-0.2BiFeO(3)were further improved by doping the material with Mn and Gd ions. This results in a composition with negligible Joule heating up to 75 degrees C and with room-temperature electrocaloric effect of more than 1 degrees C, and a high magnetocaloric effect of similar to 3 degrees C at cryogenic temperatures. Furthermore, this material also exhibits the highest room-temperature magnetocaloric effect (similar to 8 x 10(-3)degrees C) among all already known Pb(Fe0.5Nb0.5)O-3-based multicalorics.