Effects of Zr substitution on structural, morphological, and magnetic properties of bismuth iron oxide phases

The present study involves co-precipitation method to grow un-doped and Zr-doped bismuth iron oxide with x_Zr = 0.10-0.30. The molar solutions of ferric chloride (FeCl₃), zirconyle chloride (ZrOCl₂), and bismuth chloride (BiCl₃) are prepared in distilled water, and are allowed to react with sodium hydroxide (NaOH). The synthesized powders are then converted into pellets, which are sintered at 500 ℃ for two hours in a muffle furnace. X-ray diffraction (XRD) shows multi-phase formation in un-doped and Zr doped samples. Scanning electron microscope (SEM) depicts layered structure at low Zr concentration x_Zr = 0.10, while uniform surface with smaller grains and voids is observed at x_Zr = 0.20, but at x_Zr = 0.30, cracks and voids become prominent. The ferromagnetic nature of the un-doped sample is observed by vibrating sample magnetometer (VSM), while paramagnetic behavior appears due to Zr doping. The ferromagnetism in un-doped sample is lost by Zr doping, which is due to the formation of additional Fe-O-Zr bonds that induce paramagnetic behavior.