Microwave range ferrites

An alternative method which permits the microwave sintering of low-electrical-conductivity materials is secondary microwave processing. In this method. Fig. 3.20, a highly efficient microwave absorber (a susceptor) is used to heat a cavity where the sample being processed is placed (Pope, 1991). This method should allow microwave processing of a wide range of ferrites. 

The data shown in Table 2 have been extracted from experimental results of e and as a function of the frequency with typical variations shown in Figures 8 and 9 for various ceramics. In Figure 8 pronounced dipolar relaxations occur for the titanate ceramics such as barium or barium/strontium titanate in the frequency range 10 MHz - 100 GHz. The effective loss factors of these two ceramics at 2.45 GHz are 0.2 and 0.3 respectively indicating that both these materials will readily absorb microwave radiation at this industrial allocated frequency. Lime alumina silicate, steatite and calcium titanate on the other hand have loss factors below 0.02 and as such are not obvious candidates for microwave heating. Figure 10 shows the material properties of a family of ferrites, some types can have extremely high loss factors. 

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