<p>Different pre-sintering temperatures have a profound effect on the phase formation and grain activity of polycrystalline M-type hexaferrite. In this study, a conventional ceramic process was employed to synthesize polycrystalline M-type hexaferrite, BaFe₁₂O₁₉ (BaM), which was pre-sintered at 1100°C, 1150°C, 1200°C, 1250°C, and 1300°C. X-ray diffraction (XRD) analysis showed that BaM pre-sintered above 1100°C successfully formed a single-phase polycrystalline structure, and its lattice constants exhibited a gradual increase with increasing pre-sintering temperature. In addition, XRD measurements of the magnetically oriented samples revealed a high orientation factor (<i>f</i>_L), confirming the development of a strong <i>c</i>-axis-aligned crystallographic texture. The average particle size of the pre-sintered powder increased monotonically from 0.65&#xa0;μm to 1.22&#xa0;μm, and when the pre-sintering temperature was greater than 1200°C, significant agglomeration of the polycrystalline particles began to occur. The green bodies, pressed under a magnetic field, exhibited <i>c</i>-axis grain alignment. Scanning electron microscopy (SEM) images of the sintered samples show that the grain size distribution was narrower at a pre-sintering temperature of 1200°C, with fewer pores, resulting in the lowest measured porosity (6.5%). The permittivity (<i>ε</i>′) of the sintered body mainly decreased with increasing temperature, while tan<i>δ</i> remained essentially unchanged. Vibrating-sample magnetometry (VSM) measurements of the magnetically oriented sintered samples indicated that a pre-sintering temperature of 1200°C resulted in the highest magnetic anisotropy field (15,558 Oe). Overall, the sample pre-sintered at 1200°C exhibited the most uniform grain size distribution, the lowest porosity, and the highest magnetic anisotropy field, making this condition the most favorable for fabricating self-biased microwave circulators operating at high frequencies.</p>