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The hydrothermal powder preparation route is suited for achieving a very homogeneous, nanocrystalline franklinite powder. Compared to the conventional presintering via mixed oxide processing the hydrothermal route has advantages because of simplification for the powder preparation and more homogeneity caused by wet processes. As a result a prefemtized powder suspension was synthesized which can be used to obtain a granulate and pressing it to the desired core shapes. The microstructure of the sintered cores is very homogeneous and almost free of pores compared to the conventionally produced cores. Excellent magnetic properties can be achieved by sintering under considerably lower temperatures. The initial permeability resulting from sintering under the same conditions is for hydrothermal based cores app. 20 % higher.

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The combination of highly reactive raw materials with an optimized set of dopants results in high density Mn Zn ferrites. The use of non-calcined raw materials has the advantage of simplified processes and improved cost efficiency of the industrial realization. Lowest power losses and highest saturation flux densities could be achieved as a result of substantial investigations. Both properties require a dense and defect-reduced microstructure. The spinel formation and the grain growth were optimized due to the required grain size, the composition and the grain boundary thickness. Usual additive oxides like CaO, SiO 2 and Nb 2 O 5 were amended by V 2 O 5 and SnO 2 as eutectic control. Increased transport capability for the initial chlorine content of iron oxide at moderate temperatures could be enhanced by optimized shrinkage behavior. Consequently all results were adapted to commercial raw material qualities with the result of highest performance power transformer ferrites in the frequency range up to 300 kHz.

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