Study On The Synthesis Of Cerium-substituted Yttrium Iron Garnets

Cerium-substituted yttrium iron garnets (CexY3-xFe5O12, Ce :YIG), the promising materials for magneto-optical(MO) application, have been widely attended for great improvement on Faraday rotation due to the substitution of Ce3+ ions to Y3+ ions. However, studies on synthesis of Ce:YIG were restrained by two factors: the first was radium of Ce3+ ions were much larger than that of Y3+ ions, the second was Ce3+ ions tended to transfer to Ce4+ ions which were more chemically stable. In this paper, YIG and Ce:YIG were prepared via chemical synthesis method, and their composition, structure, magnetic properties were investigated.YIG and Ce:YIG precursors were prepared via coprecipitation. By means of improving homogeneity and decreasing synthesis temperature, harmful YFeO3 phase was restrained, the oxidation of Ce3+ was under control, and pure phase YIG and Ce:YIG(x=0.2) were obtained. Studies showed that process and condition control had critical effect on the preparation of YIG phase, and the proper conditions specialized as follows: using ammonia-ammonium nitrate(NH3-NH4NO3) as precipitant, PH scope from 10 to 10.5, using dissolving salt as law materials, dropping their mixed solution into precipitant, precipitation rate at 0.8ml/min. The results of X-ray powder diffraction(XRD) indicated that cubic YIG pure phase could be acquired at the synthesis temperature of 900 with stoichiometric proportion. While the doping content was not more than 0.2, Ce:YIG pure phase could be prepared at the synthesis temperature of 900. As doping content of cerium or synthesis temperature increased , CeO2 phase segregated.The constituent analysis method was developed by means of complexometric titration and oxidation reduction titration. The composition of Fe3+ and Y3+ ions were analyzed continuously and the composition of Ce3+ and Ce4+ ions was determined respectively. The results of chemical analysis were consistent with that of energy dispersion spectrophy (EDS). The results of X-ray photoelectron spectrum (XPS) demonstrated the Ce ions in pure phase Ce:YIG(x< 0.2) were in the state of trivalence.Scanning electron microscope (SEM) analysis showed conglobation of YIG and Ce:YIG particles, whose size were smaller than 1 urn. Vibrating samples magnetometer (VSM) testing implied that YIG were of ferrimagnetism, and Cerium substitution had effects on saturation magnetization(Ms), residual magnetization (Mr) and coercive force(Hc).The investigation of synthesis, composition and structure analysis, and characterization of magnetic properties of YIG and Ce:YIG would build foundation for the study of Ce:YIG single crystal in the future.