Synthesis of nanocrystalline yttrium iron garnets by sol–gel combustion process: The influence of pH of precursor solution

The nitrate–citrate gels exhibit auto-catalytic behavior, which can be used to synthesize the nanocrystalline YIG powders. In this study yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol–gel auto-combustion process. The influence of pH value of the precursor solution on the combustion behavior and the garnet phase formation of synthesized powders were investigated by scanning electron microscopy (SEM), thermal analysis (DTA/TGA), infrared (IR) spectroscopy and X-ray diffraction technique (XRD). The results show that with increasing pH value, the combustion rate increases. The as-burnt powder prepared with pH 1 yielded a single phase YIG after calcination at 800 °C, while at the pH 7 the single phase garnet were formed at higher calcination temperature (900 °C). The crystallite size of the single phase YIG prepared at pH ∼ 1 and calcined at 800 °C was ∼38 nm. In general, increasing the calcination temperature resulted in increasing the crystallite size of YIG. The calcined powders showed porous feature due to the liberation of large amount of gases during combustion.