U.S. Philips Corporation

Rudiger Jost

Heiner Kostlin

Franciscus C Van Vroonhoven

Hans Auding

Matthias Born

A discharge vessel with a ceramic wall encloses a discharge space in which besides a rare gas also an ionizable filling comprising at least NaI is present. Two electrodes having tips with a mutual distance EA are arranged in the discharge space which discharge vessel has an internal diameter Di over at least the electrode distance EA. The discharge space is Hg-free and the ionizable filling further comprises Zn and the electrode distance EA and the internal diameter Di comply with the relation 1.ltoreq.EA/Di.ltoreq.4.

Metal halide lamp

The life of light-pervious, thermal radiation-reflecting filters of tin-doped indium oxide is drastically elongated when used in oxidizing or reducing medium by coating the indium oxide layer with pyrolytic or hydrolytic silicon dioxide.

Light-pervious, heat-reflecting filter and electric lamps having such a

A light-transmitting, thermal-radiation reflecting filter which comprises a transparent support coated with indium oxide which is doped with more than 7 atomic percent of tin, calculated with respect to the number of indium atoms, has a free-electron density between 10.sup.21 and 3 times 10.sup.21 per cm.sup.3 and a plasma wavelength of less than 1.2.mu.m. The filter can be manufactured so as to have a stress-free support by heating a support, which is coated in known manner with tin-doped indium oxide, at a temperature between 300.degree.C and the softening temperature of the support material in a gas having an oxygen partial pressure of less than 10.sup..sup.-7 atmosphere.

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Aachen, Germany

Rudiger Jost