A comparative study of structural, magnetic and X-band microwave absorption characteristics of pure and Zn–Zr co-doped M-type barium hexaferrites samples

Rietveld refinement has been used to analyse phase evolution in BaFe₁₀ZnZrO₁₉ (BZFO) and BaFe₁₂O₁₉ (BFO) samples calcined between 900 °C and 1200 °C. Refinement revealed that BZFO consist of five segregated phases viz. Zn-Zr doped BFO, ZnFe₂O₄, ZrO₂, BaZrO₃ and BaFeO₃ at 1100 °C and 1150 °C. In contrast, BFO samples consist only of BFO and Fe₂O₃ phases. Both types of samples become phase pure at 1200 °C. FESEM micrographs reveal pronounced secondary grain growth in BZFO samples and reduction in grain size (0.32–0.19 µm) with dopant incorporation at 1200 °C. EDX mapping confirmed the even spatial distribution of various elements in both type of samples. VSM data reveals that BFO (H_c = 4536 Oe and M_s = 51.56 emu/g) samples exhibit superior magnetic characteristics as compared to BZFO (H_c = 728 Oe and M_s = 47.86 emu/g) samples at 1200 °C. The BFO and BZFO samples respectively show minimum RLdB values of -35.3 dB (at 8.8 GHz) and -36.6 dB (at 9.5 GHz), at 1200 °C calcination. The data suggests an enhancement in microwave absorption capacity with a) dopant incorporation and b) increase in calcination temperature.