Formation of metastable rare-earth iron garnet by splat quenching

The droplet with NdxSm3-xFe5O12 composition was undercooled in an aerodynamic levitator and splat quenched by copper anvils in order to obtain a metastable garnet with a solubility limit larger than the phase equilibrium solubility limit, x=0.375, for the NdxSm3-xFe5O12 system. The peaks of the garnet were identified with the peaks of the perovskite by powder X-ray diffraction (XRD), although the peak intensity for the garnet decreased with increasing the Nd substitution from x=0.43 to 0.2, and finally disappeared at x=2.2. When the garnet was annealed at 1570 K for 24 h in air, it transformed into a mixture of perovskite and hematite, which indicates that the garnet obtained was the metastable phase. Moreover, the amorphous phase was found in the central part of all the samples even at x=2.2, which was confirmed by micro-focus XRD. The formation of the constituent phases in the as-quenched sample was discussed using a continuous cooling transformation diagram.