Ceramic magnets (also known as ferrite magnets or hard ferrite) are developed at Philips Physics Laboratory in 1950s. They became commercially available in the 1960s due to its low cost and high magnetic performance. People call them ceramic magnets because 1) the sintering process of this magnet material is similar to ceramic and 2) both are electrically insulating. Permanent magnets really penetrated into our everyday life with the commercialization of hard ferrite. Prior to ferrite magnets, only AlNiCo magnets had dominated the permanent magnet market.
Comparing to other permanent magnets, hard ferrite has a low maximum energy product of up to 5.5MGOe. However, its high coercivity and cost-effectiveness make it an ideal magnetic material for a variety of applications. Measuring by weight, it accounts for over 75% of the global permanent magnet consumption. Ferrite arc magnet is also an important component in electric motors.
| Grade | Br | Hcb | Hcj | (BH)max | ||||
| mT | kGs | kA/m | kOe | kA/m | kOe | kJ/m3 | MGOe | |
| Y20 | 320-380 | 3.2-3.8 | 135-190 | 1.70-2.38 | 140-195 | 1.76-2.45 | 18.0-22.0 | 2.3-2.8 |
| Y22H | 310-360 | 3.1-3.6 | 220-250 | 2.77-3.14 | 280-320 | 3.52-4.02 | 20.0-24.0 | 2.5-3.0 |
| Y23 | 320-370 | 3.2-3.7 | 170-190 | 2.14-2.39 | 190-230 | 2.39-2.89 | 20.0-25.5 | 2.5-3.2 |
| Y25 | 360-400 | 3.6-4.0 | 135-170 | 1.70-2.14 | 140-200 | 1.76-2.51 | 22.5-28.0 | 2.8-3.5 |
| Y26H | 360-390 | 3.6-3.9 | 220-250 | 2.77-3.14 | 225-255 | 2.83-3.21 | 23.0-28.0 | 2.9-3.5 |
| Y27H | 370-400 | 3.7-4.0 | 205-250 | 2.58-3.14 | 210-255 | 2.64-3.21 | 25.0-29.0 | 3.1-3.7 |
| Y30 | 380-400 | 3.8-4.0 | 175-210 | 2.20-2.64 | 180-220 | 2.26-2.77 | 26.0-30.0 | 3.3-3.8 |
| Y30BH | 380-400 | 3.8-4.0 | 223-235 | 2.80-2.95 | 231-245 | 2.90-3.08 | 27.0-30.0 | 3.3-3.8 |
| Y30H-1 | 380-400 | 3.8-4.0 | 230-275 | 2.89-3.46 | 235-290 | 2.95-3.65 | 27.0-32.0 | 3.4-4.0 |
| Y30H-2 | 395-415 | 3.95-4.15 | 275-300 | 3.46-3.77 | 310-335 | 3.90-4.21 | 28.5-32.5 | 3.5-4.1 |
| Y32 | 400-420 | 4.0-4.2 | 160-190 | 2.01-2.38 | 165-195 | 2.07-2.45 | 30.0-33.5 | 3.8-4.2 |
| Y33 | 410-430 | 4.1-4.3 | 220-250 | 2.77-3.14 | 225-255 | 2.83-3.21 | 31.5~35.0 | 4.0-4.4 |
| Y35 | 400-440 | 4.0-4.4 | 176-224 | 2.22-2.8 | 180-230 | 2.26-2.89 | 30.3-33.4 | 3.8-4.2 |
| Grade | Br | Hcb | Hcj | (BH)max | ||||
| mT | kGs | kA/m | kOe | kA/m | kOe | kJ/m3 | MGOe | |
| C1 | 230 | 2.3 | 148 | 1.86 | 258 | 3.5 | 8.36 | 1.05 |
| C5 | 380 | 3.8 | 191 | 2.4 | 199 | 2.5 | 27.0 | 3.4 |
| C7 | 340 | 3.4 | 258 | 3.23 | 318 | 4.0 | 21.9 | 2.75 |
| C8 | 385 | 3.85 | 235 | 2.95 | 242 | 3.05 | 27.8 | 3.5 |
| C8B | 420 | 4.2 | 232 | 2.913 | 236 | 2.96 | 32.8 | 4.12 |
| C9 | 380 | 3.8 | 280 | 3.516 | 320 | 4.01 | 26.4 | 3.32 |
| C10 | 400 | 4.0 | 288 | 3.617 | 280 | 3.51 | 30.4 | 3.82 |
| C11 | 430 | 4.3 | 200 | 2.512 | 204 | 2.56 | 34.4 | 4.32 |
| Ceramic Magnets – Typical Physical Properties | ||
| Property | Units | Value Ceramic (Strontium Ferrite) |
| Vickers Hardness | Hv | ~ 1160 (7 Mohs) |
| Density | g/cm3 | 4.5 to 5.1 |
| Curie Temp TC | °C | 450 to 460 |
| Curie Temp TF | °F | 840 to 860 |
| *Specific Resistance | μΩ⋅Cm | > 106 |
| Bending Strength | kN/mm2 | 0.05 – 0.09 |
| Tensile Strength | kN/mm2 | .02 to .05 |
| Thermal Expansion (∥) | °C-1 | +11.0 to +16.0 x10-6 |
| Thermal Expansion (⊥) | °C-1 | ‘+7.0 to +15.0 x 10-6 |
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