Study On Magnetocaloric Effect Of Barium Titanate

Artificial refrigeration technology is an important symbol of industrial civilization in modern society and plays a crucial role in human life and production.Cryogenic refrigeration technology in space science and helium,hydrogen liquefaction technology has important application value,so the research of cryogenic magnetic refrigeration material is more and more extensive.In recent years,rare earth metal oxides have become the new research focus in the field of magnetic refrigeration materials because of their simple preparation,relatively stable chemical properties,large-scale production,easy processing and molding,and low cost.In this paper,the magnetic and magnetocaloric effects of perovskite rare earth metal oxides Eu_1-xSr_xTiO₃,Eu_0.9La_0.1TiO₃,Eu_0.9Ce_0.1TiO₃,EuTi_1-xCo_xO₃ and EuTi_1-xMn_xO₃ were studied.The main results are as follows:?1?With slight Sr-doping,the AFM ordering of pure EuTiO₃ can be significantly changed to be FM due to lattice parameters changed.A giant reversible MCE and large RC for Eu_1-xSr_xTiO₃ compounds were observed.The values of-?S_M^max are evaluated to be around 10 and 21 J/kg K under the magnetic field changes of 1 and 2 T.the values of-?S_M^max of Eu_1-x-x Sr_xTiO₃ compounds do almost no change,but,the values of RC are increased as Sr substituting to Eu.The values of RC are evaluated to be 36.6,107.8 and308.6 J/kg for Eu_0.9Sr_0.1TiO₃ under the magnetic field changes of 1,2 and 5 T.?2?A giant reversible magnetocaloric effect and magnetic properties in Eu_0.9R_0.1TiO₃?R=La,Ce?have been investigated.The antiferromagnetic ordering of pure EuTiO₃ can be significantly changed to be ferromagnetic as substitution of La?x=0.1?and Ce?x=0.1?ions for Eu²⁺ions.When the part of Eu²⁺ions were substituted by La³⁺and Ce³⁺ions,there is a slight excess of oxygen in the Eu_0.9R_0.1TiO₃?R=La,Ce?,which could compensate the mismatch of chemical valence and increase the lattice constant.The large low-field enhancements of-?S_M and RC for Eu_0.9La_0.1TiO₃ and Eu_0.9Ce_0.1TiO₃?-?S_M=10.8 J/kgK,RC=51.8 J/kg and-?S_M=11 J/kgK,RC=39.3 J/kg for at magnetic field change of 10kOe?relative to pure EuTiO₃ counterpart?-?S_M=9.8 J/kg K,RC=27 J/kg?.The increase of-?S_M and RC can be attributed to magnetic phas.?3?EuTi_1-xCo_xO₃ and EuTi_1-xMn_xO₃ compounds were synthesized.By XRD analysis,the compounds EuTi_1-xCo_xO₃ and EuTi_1-xMn_xO₃ are single-phase cubic perovskite structures.When Ti⁴⁺ions are replaced by Co²⁺and Mn²⁺ions,their lattice constants will change due to their different ion sizes.The delicate balance of AFM and FM phases in the EuTiO₃ compound changes.The value of-?S_M^max of EuTi_0.95Co_0.05O₃ can reach 10 J/kg K and the value of RC reach 38.5 J/kg with the change of magnetic field?0-10?kOe,and the value of-?S_M^max of EuTi_1-x-x Mn_xO₃ is also larger than 10 J/kg K.