Research About The Phase Transition Correlation Of Magnetic Functional Material Mn₃GaC

Anti-perovskite Mn₃Ga C has attracted more and more attention because of its simple structure,rich physical properties and potential application prospects.The good magneto-thermal effect near the phase transition point is the main research content of this material.The magnetic entropy and hysteresis near the first phase transition are large,but the effective cooling capacity is small.The low temperature phase transition point and narrow phase transition temperature limit the application range of the material.In this paper,starting from the study of magneto-thermal effect of Mn₃Ga C,a series of doped materials were prepared by mixing different metal elements and rare earth elements,changing the"spin"configuration of the material,regulating its magnetic structure,changing the phase transition type and phase transition point,and broadening the phase transition temperature region of the material,so as to achieve the purpose of controllable magneto-thermal effect.Mn the perovskite compound material of conductive performance can be compared with the metal material,but its valence bond structure has been not clear,whether this kind of material is a semiconductor material or metal materials has not yet been determined,finally,the paper explored the system by optical characterization means material combination of key information,to determine the properties of materials,has played an important role in application scope.Based on references and experimental methods,the required metal elements and rare earth elements were screened out to prepare a series of doping materials.In this project,by selecting appropriate raw material ratio and optimizing sintering process,high purity doping raw materials were synthesized,and finally Mn₃Ga_1-xSn_xC(x=0,0.05,0.1,0.15,0.2,0.8,0.9,1)series compounds were synthesized.The phase transition temperature zone of the series compounds continued to move to the low temperature zone.But the entropy stays constant.On the basis of this,the related properties were explored.At the same time,the corresponding composites were synthesized by means of physical recombination according to the equal molar ratio.The composite material showed an approximate platform-like magnetic entropy change curve near room temperature.Compared with Mn₃Sn C,the half-height-width curve and refrigerant capacity(RCP)have been significantly improved.The composite material is beneficial to the magnetic Erikson cycle and provides a new method for the research of composites and the development of practical magnetic refrigerants.Mn₃Ga_1-xA_xC(A=Y,Ge)series compounds were synthesized by selecting appropriate raw material ratio and optimizing sintering process.The phase transition point and phase transition interval were regulated by doping method,so as to better control the application interval of its magneto-thermal effect.In order to analyze the material type,the photoluminescence spectra,Fourier transform infrared spectra and UV-Vis absorption spectra of Mn₃Ga_1-xA_xC series materials were measured.Optical test found that the material showed no obvious optical band gap in the visible light range,and all the spectra in the visible light range were similar to those measured without the sample.The material is also not photoluminescent.Mn ion has photoluminescence characteristics.Optical test shows that Mn and other elements in perovskite do not exist in the form of ions,and the bonding bond in the material is not mainly ionic bond.The material does not have electron,rotational and vibrational energy level transitions,and it has the same absorption to all visible light bands,showing metal properties,and the bonding bonds are mainly metal bonds.This class of materials is a class of intermetallic compounds with metallic properties.