Abstract: The invention relates to a luminescent material of general formula (BaxSr1−x−yPby)2Mg(BO3)2 wherein 0≦x≦0.999, 0.0005<y<0.05. Luminescent materials of this general formula are very suitable for use in low pressure mercury discharge lamps for tanning purposes.

Abstract: A low-pressure mercury discharge lamp with a lamp vessel having a first lamp vessel portion (La1) with a first electrode (E11) and a first luminescent layer which radiates white light of a first color temperature during lamp operation and a second lamp vessel portion (La2) with a second electrode (E12) and with a second luminescent layer which radiates white light of a second colour temperature different from the first during lamp operation. The first lamp vessel portion and the second lamp vessel portion are interconnected by a connection which allows a filling of mercury and a rare gas in both portions to pass and together enclose a discharge space. The discharge space contains only one further electrode (E13) for both the first and second lamp vessel portions.

Abstract: A method of selecting low-pressure mercury discharge lamps comprising a luminescent layer, the luminescent layer being excited and the low-pressure mercury discharge lamps being selected in dependence on the emission spectrum of the visible light emitted by the luminescent layer. The luminescent layer is excited by a light source arranged outside the low-pressure mercury discharge lamp and which generates ultraviolet radiation having a wavelength above 300 nm. This makes it possible to use the presence of a blue-luminescent substance in the luminescent layer as a selection criterion for both leaky and intact low-pressure mercury discharge lamps.

Abstract: The invention relates to a high-pressure sodium discharge lamp which under nominal operating conditions radiates white light with a maximum color rendering index R.sub.a of more than 80. Since the wall load is above 80 W/cm.sup.2 under nominal operating conditions, a color temperature T.sub.c of at least 2800.degree. K. can be achieved with a luminous efficacy of more than 40 lm/W.

Abstract: A low-pressure mercury vapor discharge lamp having a very satisfactory color rendition, (R(a,8).gtoreq.85), a color temperature of 2300-3300 K and a color point on or near the Planckian curve. The lamp is provided with a luminescent layer comprising:a. a luminescent alkaline earth metal halophosphate activated by Sb.sup.3+ and Mn.sup.2+ having a color temperature of 2900-5000 K;b. a luminescent material activated by Eu.sup.2+ with an emission maximum van 470-500 nm and a half-value width of at most 90 nm, andc. a luminescent rare earth metal metaborate activated by Ce.sup.3+ and Mn.sup.2+, having a fundamental lattice Ln(Mg,Zn,Cd) B.sub.5 O.sub.10, in which Ln represents the elements Y, La and/or Gd, which borate has red Mn.sup.2+ emission.Further, the lamp is provided with means for absorbing blue radiation having wavelengths below 480 nm. Preferably, the luminescent layer further contains:d. a luminescent material activated by Tb.sup.3+ which exhibits green Tb.sup.3+ emission.

Abstract: A low-pressure mercury vapor discharge lamp having a very satisfactory color rendition (R(a,8).gtoreq.85) and having a color temperature of at least 3200 K. and a color point located on or near the Planckian locus. The lamp is provided with a luminescent layer comprising:a. a luminescent alkaline earth metal halophosphate activated by Sb.sup.3+ or by Sb.sup.3+ and Mn.sup.2+b. a luminescent material activated by Eu.sup.2+ and having an emission maximum at 470-500 nm and a half-width value of at most 90 nm andc. a luminescent rare earth metal metaborate activated by Ce.sup.3+ and Mn.sup.2+ and having a fundamental lattice Ln(Mg,Zn,Cd)B.sub.5 O.sub.10, where Ln represents the elements Y, La and/or Gd, which borate has a red Mn.sup.2+ emission.

Abstract: A low-pressure mercury vapor discharge lamp having a satisfactory color rendition (Ra.gtoreq.80), a color temperature of 2800.degree. K. or higher and a color point on or near the Planckian locus. The lamp is provided with a luminescent layer (4) which comprisesa. a luminescent rare earth metal metaborate activated by Ce and Mn and having a fundamental lattice Ln(Mg,Zn,Cd)B.sub.5 O.sub.10, where Ln represents the elements Y, La and/or Gd, which borate exhibits red Mn emission,b. a luminescent material activated by Tb.sup.3+ and having green Tb.sup.3+ emission,c. at least one luminescent halophosphate of the group which comprises the calcium halophosphates emitting white light, activated by Sb.sup.3+ and Mn.sup.2+ and having a color temperature of at least 2900.degree. K. and blue-luminescing calcium halophosphate activated by Sb.sup.3+.The lamps yield a satisfactory rendition of deep red colors (R9.gtoreq.60) and have a high luminous flux and a high maintenance of the luminous flux during the life.

Abstract: Luminescent material having a host lattice comprising, as one of the main constituents, at least one of the elements Y, La and the lanthanides. The material is activated by Gd, and, in addition by one or more of the elements Pb, Tl, Sb, Pr and Bi and comprises one or more of the elements Mn, Tb, Eu, Dy and Sm and the third activator. These materials have an efficient emission originating from the third activator and are used in low-pressure mercury vapour discharge lamps.