Ceramic Magnets Technical Information
| Isotropic | Anisotropic | |||
| Magnetic Characteristics | Duramax 1 | Duramax 5 | Duramax 8 | |
| Residual Induction Br |
(G) | 2200 | 3950 | 3900 |
| (mT) | 220 | 395 | 390 | |
| Coercive Force Hc | (kOe) | 1800 | 2400 | 3200 |
| (kA/m) | 190 | 255 | ||
| Intrinsic Coercive Force Hcl | (kOe) | 3000 | 2450 | 3250 |
| (kA/m) | 195 | 260 | ||
| Maximum Energy Product BHmax | (MGOe) | 1.05 | 3.6 | 3.5 |
| (kJ/m³) | 28.6 | 27.8 | ||
| Magnetic Characteristics | Duramax 1 | Duramax 5 | Duramax 8 | |
| Density | (lbs/in³) | .177 | .178 | .176 |
| (g/cm³) | 4.9 | 4.8 | ||
| Curie Temperature | °F | 842 | 842 | 842 |
| °C | 450 | 450 | 450 | |
| Maximum Operating Temperature | °F | 480 | 480 | 480 |
| °C | 250 | 250 | 250 | |
Ceramic (Duramax) Manufacturing Processes
Ceramic magnets are manufactured by calcining or presintering a mixture of iron oxide and strontium ferrite to produce a metallic oxide. A multiple stage milling operation reduces the calcined material to a small particle size; this finely milled water borne powder is then compacted in the presence of a magnetic alignment field to a "green" state. These compacted parts, which approximate the finished geometry, are then sintered at high temperatures to achieve the final fusion of the individual particles. Parts which have been produced in this manner are anisotropic and will exhibit a preferred direction of orientation when magnetized. Final shaping of this material is accomplished by grinding with diamond abrasives. Normally, ceramic magnets will not only be ground on the pole faces; all remaining surfaces will exhibit as sintered tolerances and physical characteristics.
Temperature Characteristics of Ceramic Magnets
If the Ceramic materials are required to operate at temperatures other than ambient, consideration must be given to the effects on the magnet's performance. Normally temperature ranges above ambient do not result in any permanent losses unless they approach the Curie point for that given grade of material. Elevated temperatures do have a temporary effect on the performance of the magnet and these losses must be considered when designing a particular circuit. Excursions below ambient temperatures may result in permanent losses if the circuit has not been designed to account for such extremes. The grade of material, temperature extremes, magnet geometry, and circuit configuration will all influence the ability of a given device to withstand adverse thermal conditions without permanent losses. Please consult the individual product data sheets for specific temperature data or consult our application engineering staff for additional information.
Physical Characteristics of Ceramic Magnets
The crystalline structure of the ferrite material makes drilling, threading or machining of the magnet impractical. The mechanical characteristics of this material prevent them from being utilized where impact or flexing may be experienced. As with most ceramics, the ferrite materials should not be exposed to heating or cooling rates greater than (200°F per hour). This will minimize the possible effects of thermal shock which can result in physical damage to the part. Imperfections such as chips, cracks, or similar characteristics are commonly found on sintered ferrite magnets. Duramag works with its customers to develop a mutually agreed upon visual inspection standard to insure that only acceptable physical characteristics are present in the final products supplied.