Studies On Preparation And Properties Of YFeO₃ Powders And Ceramics

Currently, YIG crystals, the most widely used magneto-optical material have the shortcoming of a small Faraday rotation angle and high saturation magnetization, it is not beneficial to the miniaturization and integration of the device. Yttrium ferrite (YFeO3) is an excellent magneto-optical material compare with YIG. having broad promising application on optical fiber communications, especially magneto-optical devices, but the preparation of YFeO3 single crystal is difficult and expensive. Textured ceramics have similar anisotropy as single crystals, and even may make the ceramics performance equivalent to that of single crystals’, therefore, the research and development of YFeO3 texture ceramics are very significant.In this paper, YFeO3 polycrystalline powders prepared by combustion synthesis method and YFeO3 plate grains synthesized by hydrothermal method were used as matrix powders and templates, respectively. The YFeO3 green tapes were made by the technique of template grain growth (TGG) and tape-casting method. The YFeO3 textured ceramics were prepared by the lamilating technique of green tapes and sintering. The influence factors of the preparation of YFeO3 by combustion synthesis and hudrothermal method were invetigated. The effects ratio of raw materials and technological parameters on the phase compositions and microstructure were discussed. The influences of composition of tape-casting slurry on the properties of slurry were studied. The approprate recipe of slurry was obtained. The effects of technological parameters such as sintering temperatures and sintering time on the density and microstructure were researched. YFeO3 textured ceramics were prepared. The results are as follows:Firstly, single phase YFeO3 particles with 80～100nm size were successfully synthesized by adjusting the amount of urea and ammonium nitrate as well as the heating temperature by combustion synthesis method using Y(NO3)3, Fe(NO3)3 and CO(NH2)2 as raw materials.Secondly, YFeO3 grains with the square plate were prepared by hydrothermal method by adjusting the concentration of potassium hydroxide in reaction solution and reaction time, using Y2O3, Fe(NO3)3 and nitric acid as raw materials and KOH as a mineralizer. The size increased with the extention of time. The side length of square grains 2.5μm and thick of 400nm at 24h while the valuea are 5.2μm and 1.5μm at 72h, respectively.Thirdly, the optimum composition of slurry was prepared with solids content of 65wt.%, dispersant content of 0.5wt.%, binder of 10wt.% and 6wt.% of plasticizer, through optimizing the experiment program.Finally, YFeO3 trxture ceramics were prepared through investigating the effects of sintering parameters on densities, microstructure and properties. The appropriate sintering condition to prepare relatively dense ceramic was that sintering temperature was 1450℃ and duration time was 8h, and the suitable sintering additive was Er2O3 and optimal dosage was 0.5wt.%.