Figure 1. X-ray diffraction patterns of (a) SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2), (b) Sr1−yFe12−ySiyKyO19 (y = 0, 0.05, 0.1, 0.2), (c) SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.1, 0.2, 0.4, 0.6), and (d) SrFe12−xSixO19 (x = 0, 0.1) samples sintered at 1250 °C.

Figure 1. X-ray diffraction patterns of (a) SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2), (b) Sr1−yFe12−ySiyKyO19 (y = 0, 0.05, 0.1, 0.2), (c) SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.1, 0.2, 0.4, 0.6), and (d) SrFe12−xSixO19 (x = 0, 0.1) samples sintered at 1250 °C.

Figure 2. (a–c) XRD patterns with Rietveld refinement for SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.4) samples.

Figure 2. (a–c) XRD patterns with Rietveld refinement for SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.4) samples.

Figure 3. Change (%) in the lattice parameters a, c, and cell volume of (a) SrFe12−2xSixMgx, (b) Sr1−yFe12−ySiyKy, and (c) SrFe12−z(Li0.6Si0.6)z samples sintered at 1250 °C.

Figure 3. Change (%) in the lattice parameters a, c, and cell volume of (a) SrFe12−2xSixMgx, (b) Sr1−yFe12−ySiyKy, and (c) SrFe12−z(Li0.6Si0.6)z samples sintered at 1250 °C.

Figure 4. SEM micrographs of the (a–d) SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2), (a,e–g) Sr1−yFe12−ySiyKyO19 (y = 0, 0.05, 0.1, 0.2), and (a,h–l) SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.1, 0.2, 0.4, 0.6) samples sintered at 1250 °C.

Figure 4. SEM micrographs of the (a–d) SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2), (a,e–g) Sr1−yFe12−ySiyKyO19 (y = 0, 0.05, 0.1, 0.2), and (a,h–l) SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.1, 0.2, 0.4, 0.6) samples sintered at 1250 °C.

Figure 5. M-H curves of (a) SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2) and (b) SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.1, 0.2, 0.4, 0.6) samples sintered at 1250 °C, and (c,d) plots of MS and HC vs. x and vs. z. Here, the MS value is defined as the magnetization (M) value at H = 2.5 kOe.

Figure 5. M-H curves of (a) SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2) and (b) SrFe12−z(Si0.6Li0.6)zO19 (z = 0, 0.05, 0.1, 0.2, 0.4, 0.6) samples sintered at 1250 °C, and (c,d) plots of MS and HC vs. x and vs. z. Here, the MS value is defined as the magnetization (M) value at H = 2.5 kOe.

Figure 6. Demagnetization curves (4πM-H) of (a) SrFe11.95Si0.03Li0.03O19 and (b) Sr0.8La0.2Fe11.75Co0.2Si0.03Li0.03O19 samples sintered at 1230 °C with various sintering additives.

Figure 6. Demagnetization curves (4πM-H) of (a) SrFe11.95Si0.03Li0.03O19 and (b) Sr0.8La0.2Fe11.75Co0.2Si0.03Li0.03O19 samples sintered at 1230 °C with various sintering additives.

Figure 7. Demagnetization curves (4πM-H and B-H) of the anisotropic magnets, SrFe11.95Si0.03Li0.03O19 and Sr0.8La0.2Fe11.75Co0.2Si0.03Li0.03O19, sintered at 1230 °C.

Figure 7. Demagnetization curves (4πM-H and B-H) of the anisotropic magnets, SrFe11.95Si0.03Li0.03O19 and Sr0.8La0.2Fe11.75Co0.2Si0.03Li0.03O19, sintered at 1230 °C.

Table 1. The lattice parameters a, c, c/a ratios, and lattice volumes (vol.) of the SrFe12−2xSixMgx, Sr1−yFe12−ySiyKy, and SrFe12−z(LizSiz)0.6 samples sintered at 1250 °C.

Table 1. The lattice parameters a, c, c/a ratios, and lattice volumes (vol.) of the SrFe12−2xSixMgx, Sr1−yFe12−ySiyKy, and SrFe12−z(LizSiz)0.6 samples sintered at 1250 °C.

Compositionx, y, za (Å) c (Å) c/a vol. (Å3) SrFe12−2xSixMgxO1905.88523.0553.917691.500.055.87923.0593.922690.210.15.88123.0723.923691.060.25.87023.0923.934689.02Sr1−yFe12−ySiyKyO190.055.88323.0793.923691.740.15.88223.0663.921691.170.25.88023.0763.925690.90SrFe12−z(Si0.6Li0.6)zO190.055.88423.0563.919691.200.15.88223.0663.921691.190.25.88123.0753.924691.090.45.87823.0763.926690.530.65.88023.0833.926691.18

Table 2. The sintered sample density (ρ), saturation magnetization (Ms), and coercivity (HC) of hexaferrite samples, SrFe12−2xSixMgx and SrFe12−z(LizSiz)0.6 sintered at 1250 °C. The error bar for MS is ± 0.2% and for HC is ±1% of the original values.

Table 2. The sintered sample density (ρ), saturation magnetization (Ms), and coercivity (HC) of hexaferrite samples, SrFe12−2xSixMgx and SrFe12−z(LizSiz)0.6 sintered at 1250 °C. The error bar for MS is ± 0.2% and for HC is ±1% of the original values.

Compositionx, zρ (g/cm3)MS (emu/g)HC (Oe)SrFe12−2xSixMgxO1902.7572.0835620.052.8772.1539120.12.9170.4634020.24.0766.492986SrFe12−z(LizSiz)0.6O1902.7572.0835590.053.0973.9237130.13.2472.3633930.23.2370.539040.43.9070.738090.63.8464.153216

Table 3. The sintered sample density (ρ), remanent magnetization (Br), and coercivity (HC) of hexaferrite samples SrFe11.95Li0.03Si0.03O19 and Sr0.8La0.2Fe11.75Co0.2Li0.03Si0.03O19 with different additives sintered at 1230 °C.

Table 3. The sintered sample density (ρ), remanent magnetization (Br), and coercivity (HC) of hexaferrite samples SrFe11.95Li0.03Si0.03O19 and Sr0.8La0.2Fe11.75Co0.2Li0.03Si0.03O19 with different additives sintered at 1230 °C.

CompositionAdditivesρ (g/cm3)Br (G)HC (Oe)SrFe11.95Li0.03Si0.03O19SrCO3 0.5wt%4.9226292878SrCO3 0.75 wt%4.9326312554SrCO3 1 wt%5.0424591810SrCO3 0.5 wt% + CaCO3 0.5 wt%5.0425962129SrCO3 1 wt% + SiO2 0.5 wt%4.7025094149SrCO3 1 wt% + Co3O4 0.5 wt%5.0423751914CaCO3 1 wt% + SiO2 0.5 wt%4.8025284165Sr0.8La0.2Fe11.75Co0.2Li0.03Si0.03O19SiO2 0.5 wt% + SrCO3 1.0 wt%4.6824204786SiO2 0.5 wt% + CaCO3 1.0 wt%4.9225824608

Table 4. The magnet density, intrinsic coercivity (iHC), coercivity in BH (bHC), remanence magnetic flux density (Br), and maximum energy product (BHmax) of the sintered anisotropic magnets.

Table 4. The magnet density, intrinsic coercivity (iHC), coercivity in BH (bHC), remanence magnetic flux density (Br), and maximum energy product (BHmax) of the sintered anisotropic magnets.

Magnet Compositionρ
(g/cm3)iHC
(Oe)bHC
(Oe)Br
(G)BHmax
(M·G·Oe)SrFe12O194.953182300242074.24SrFe11.95Li0.03Si0.03O194.943206300943144.46Sr0.8La0.2Fe11.75Co0.2Li0.03Si0.03O195.023897313842933.98