Abstract: In a thin film electroluminescent element comprising a phosphor thin film, a dielectric thin film disposed on at least one of the surfaces of the phosphor thin film and electrodes for applying a voltage across the thin films, the aforementioned dielectric thin film is formed of a dielectric material expressed by a general formula of AB.sub.2 O.sub.6 (where A represents a divalent metal element and B represents a pentavalent metal element). By employing the dielectric material, the voltage for driving a thin film electroluminescent element can be lowered without decreasing the brightness of the element. Further, by using a composite dielectric thin film in which the dielectric thin film expressed by the aforementioned general formula AB.sub.2 O.sub.6 is laminated with a dielectric thin film which is not susceptible to dielectric breakdown of self-healing type, the composite dielectric thin film is made susceptible to the dielectric breakdown of self-healing type.

Abstract: A fluorescent display device comprising at least one phosphor screen composed of a mixture of a SnO.sub.2 :Eu phosphor with at least one of the cathodoluminescent phosphors having emission spectra and exitation properties different from SnO.sub.2 :Eu phosphor. This fluorescent display device emits light of different colors when driven at different voltages and at pulse voltages of different duty cycles. A display apparatus comprises such a fluorescent display device and a driving device with variable output voltage.

Abstract: In a method of making a magnetic gap by depositing a glass layer on a surface of magnetic head core materials by cathodic sputtering of a glass target and cementing a pair of the resulting glass-coated magnetic head core materials, the improvements constituted by monitoring the thickness of the sputtered glass layer by an interference of a light beam guided onto a surface of the magnetic head core materials during the deposition and using a sputtering apparatus having a sample holder beside the target for securing the magnetic core materials and a mask plate for achieving uniform thickness of the sputtered glass layer.The method makes possible production of magnetic heads having excellent electromagnetic conversion characteristics with high accuracy.