Abstract: Phosphor lag was reduced to acceptable levels in high lag monoclinic M' yttrium tantalate x-ray phosphors through the addition of minor amounts europium to the phosphors. In particular, europium was added to yttrium tantalate phosphors containing terbium and to phosphors formulated with a stoichiometric excess of yttrium.

Abstract: The present invention provides a process for the preparation of a small particle size borate lamp phosphor by preparing a dispersed suspension containing particles of a borate lamp phosphor precursor, adding a sufficient amount of boric acid to the dispersed suspension to provide for the mutual isolation of the borate lamp phosphor precursor particles in the boric acid, drying the mixture under conditions suitable for retaining the precursor as a dispersed phase in a matrix of boric acid, communicating the dried mixture, firing the comminuted mixture under conditions suitable for converting the precursor to a small particle size borate lamp phosphor product in a matrix of boric oxide while maintaining the mutual isolation of the product particles, and contacting the resulting mixture with water to solubilize substantially all of the boric oxide and separate the small particle size borate lamp phosphor product.

Abstract: An improved mercury vapor discharge lamp is disclosed. The lamp of the present invention includes an envelope and a selectively reflecting silicon dioxide layer on at least a portion of the inner surface of the envelope. The lamp further includes a phosphor coating disposed on the selectively reflecting layer. The silicon dioxide layer has a coating weight of from about 0.1 to about 4 mg/cm.sup.2. The selectively reflecting layer comprises at least about 80 weight percent silica having a primary particle size from about 5 to about 100 nm with at least about 50 weight percent of the silica having a primary particle size from about 17 to about 80 nm.