| The research of Multiferroic materials in information storage,magnetoelectric coupling,sensor parts,etc have great important value.Multiferroic materials have great significance for new functional materials including complex magnetoelectric effects,relationship between magnetism and electrical properties and revealing new functional materials.In the study of single-phase multi-ferroic materials,the properties of YCrO3 and YFeO3 and their mutual doping has attracted many scholars.This thesis give a systematic study of microstructure,thermal analysis,magnetic properties and photocatalytic properties for YCrO3,YFeO3 and YFe1-xCrxO3 solid solution.The main contents of the thesis are as follows:1.The YFeO3 powders were prepared by sol-gel method.A hexagonal phase YFeO3 sample(h-YFO)was obtained by calcination at 675℃ for 10h,and calcined at 750℃ for 10hto obtain a sample(m-YFO)in which hexagonal phase YFeO3 and orthogonal phase YFeO3 were both exist When the temperature rises to 850℃,a completely pure orthogonal perovskite structure phase(o-YFO)is obtained.The more crystalline,orthogonal phase YFeO3 is smaller in size than the hexagonal phase YFeO3 of the thermal metastable state.At room temperature,the initial concentration of h-YFO,m-YFO and o-YFO was 10 mg/L rhodamine B in the presence of photocatalyst and H2O2,and the degradation efficiencies were 36.7%,25.1%and 18.4%.YFe03 has a typical hysteresis loop at room temperature,the macroscopic magnetic properties of the orthogonal phase YFeO3 powders were the most obvious,the saturation magnetization and coercive force respectively were 1.356emu·g-1 and 12.62kOe.2.YFe1-xCrxO3(0.6≤ x ≤1)powder oxide of orthogonal perovskite structure was prepared by solid phase method at 1350℃ for 4 h.The Nell temperature of YCrO3 is 140k,with the increase of Fe3+ doping amount to x=0.6,the Neil temperature rises from 140k to 209k, antiferromagnetic is more obvious at low temperatures,the saturation magnetization decreases from 1.699emu·g"1 to 0.446emu·g-1.YCrO3 undergoes magnetic phase transition at 140k.Due to the non-180° spin of Cr-O-Cr,the weak ferromagnetism is not completely offset.Doping of Fe3+induces magnetization reversal and negative magnetization at low temperatures, YFe0.4Cr0.6O3 exhibits magnetization reversal at around 55k,and YFeo0.2Cr0.8O3 exhibits magnetization reversal at 149k and 86k,the compensation temperature is Tcomp～128k.The possible reason for the magnetization reversal is that the effects of single crystal magnetic anisotropy and DM on ion spins are different in different temperature ranges,resulting in magnetization reversal and negative magnetization at a special ratio of Fe3+ doping.3.YFe1-x CrxO3(0≤x≤0.4)powders were prepared by sol-gel method,the orthorhombic perovskite structure YFe1-xCrxO3(0≤x≤0.4)powder can be obtained at 850℃.After low concentration(x=0.1,0.2)Cr3+doping,the synthesis temperature of the orthogonal phase YFe1-xCrxO3 solid solution is reduced,and the orthogonal phase YFe1-xCrxO3 solid solution can be synthesized by calcination at 675℃ for 10 h.After high concentration(x=0.3,0.4)Cr3+doping,the YFe1-xCrxO3 solid solution at 675℃ for 10 h is amorphous,indicating that the high concentration of Cr3+ doping increases the synthesis temperature.The interplanar spacing,unit cell parameters,unit cell volume and grain size decrease with increasing Cr3+ doping ratio.At room temperature,YFe1-xCrxO3(0≤ x ≤0.4)powder and catalytic aid H2O2 were photocatalyzed by 10mg/L Rhodamine B solution.After 80min,the degradation rate of YFeO3,YFe0.9Cr0.1O3 and YFe0.7Cr0.3O3 were 36.7%,24.5%and 19.4%respectively.The VSM test was carried out on different ratios of YFe1-xCrxO3 solid solution.With the increase of doping concentration,the saturation magnetization and coercivity decreased gradually. |
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