US Patent 10236174 Lumen maintenance in fluorescent lamps

A fluorescent lamp, including a vitreous portion of the fluorescent lamp comprising a vitreous envelope filled with a working gas mixture, the vitreous envelope having an inner surface facing the working gas mixture side of the vitreous portion; a first coating deposited on the inner surface, the first coating comprising a first metal oxide; a second coating deposited on top of the first coating, the second coating comprising a phosphor; and a third coating deposited on top of the second coating, the third coating comprising a second metal oxide.