A method for the fabrication of thin ceramic sheets for use as capacitor dielectrics is described. Electrical tests indicate that titanium dioxide and various titanate sheets so prepared are desirable for such applications.A machine is described which extrudes a ceramic slip with a resin binder on a moving belt. The thin sheet is strong enough when dry to be stripped off and cut or punched to any desired flat shape and fired satisfactorily. The electrical properties of the material so produced have been determined and the assembly of the sheets into capacitors is discussed.

The growth of single crystals corresponding to x=0 (high-purity magnetite), x -0 0 1 and x -0 0 4 in the composition series Co x Fe3_^O4 is described. First-and second-order anisotropy constants of these crystals are determined by the torque method over the temperature range 120-450° K. The substitution of small amounts of cobalt for iron is found to add a positive contribution to K\ and a negative contribution to Kt. At low cobalt concentrations the magnitude of this contribution is a linear function of the amount of cobalt added. It is suggested that the effect of cobalt on the anisotropy is enhanced by the presence of divalent iron in magnetite, and it is concluded that the change in sign of AT in magnetite at about 130°K is not caused by the presence of cobalt or any other foreign impurity.LIST OF SYMBOLS W A = Magnetocrystalline anisotropy energy per unit volume, erg/cm 3 . Ki -First-order anisotropy constant, erg/cm 3 . K 2 = Second-order anisotropy constant, erg/cm 3 . K' = Uniaxial anisotropy constant, erg/cm 3 . <*i > a 2> a 3 -Direction cosines of magnetization with respect to cubic crystal axes, [hkl] = Crystallographic direction designated by Miller indices h, k and 1. (hkl) = Crystallographic plane whose normal is designated by Miller indices h, k and 1. x = Mol fraction of cobalt ferrite in solid solution with magnetite.

The abnormal plots of reduced magnetization vs temperature for ferrites containing zinc are found to be associated with a concentration gradient in zinc that is generated by the preferential loss of zinc during sintering. The variation of the gradient in samples of zinc-iron spinels is correlated with sintering and annealing treatment and with sample dimensions.

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