Abstract: A highly dense transparent aluminum oxide (alumina) has a fine crystal size and is stabilized for use at temperatures of 800° C. or more. Structures thereof may be used in the lighting industry in, for example, an electric lamp having a discharge tube with a wall of such a ceramic. The alumina according to the invention is provided with an additive comprising an oxide of yttrium, erbium or lanthanum and has an average crystal size ?2 ?m, and a relative density higher than 99.95% with a real in-line transmission RIT ?30-50%, measured over an angular aperture of at most 0.50 at a sample thickness of 0.8 mm and with a single wave-length of light of, preferably, 645 nm.

Abstract: An electric lamp is disclosed comprising a light-transmitting lamp vessel (1) which accommodates a light source (2). At least a part of the lamp vessel (1) is provided with a light-absorbing coating (3), the light-absorbing coating comprising stabilized pigments which are incorporated in a sol-gel matrix. In order to stabilize the pigments, an aminosilane is present. Moreover, a lamp vessel (1) fit for an electric lamp is disclosed, as well as a method of preparing a light-absorbing layer to be applied to the lamp vessel of an electric lamp.

Abstract: The invention relates to highly dense transparent aluminum oxide (alumina) and structures thereof for applications where, e.g. in the lighting industry, a fine crystal size has to be obtained and stabilized for use at temperatures of 800° C. or more. The invention also relates to an electric lamp having a discharge tube with a wall of such a ceramic. The alumina according to the invention is provided with an additive and has an average crystal size=2 ?m, and a relative density higher than 99.95% with a real in-line transmission RIT=30%, preferably >40% and more preferably >50%, measured over an angular aperture of at most 0.50 at a sample thickness of 0.8 mm and with a single wave-length of light ? of preferably 645 nm, and the additive comprises at least one of the substances from the group consisting of oxides of Mg, Y, Er and La.