Cerium and terbium activated aluminate phosphors
US4026816A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 17, 1975 |
| Grant date | May 31, 1977 |
| Priority date | — |
| Expiry date | Jan 17, 1995 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC09K11/7774
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
Phosphors having useful fluorescent emission properties comprise aluminates of magnesium, zinc and/or lithium having an hexagonal or so-called ".beta.-alumina" crystal structure and activated by cerium and terbium. In preferred phosphors the ratio of Mg:Al is from 0.01 to 0.5:1, Ce:Al from 0.001 to 0.1:1 and Tb:Al from 0.005:1 to 0.25:1. Where zinc or lithium wholly or partially replace the magnesium, chemically equivalent amounts may be used. A particularly useful phosphor conforms substantially to the approximate formula (Ce,Tb).sub.1 Mg.sub.1.sub.-2 Al.sub.22 O.sub.x, where x is the number of atoms of oxygen required to satisfy the valencies of the metals. The invention also provides a valuable process for the preparation of such aluminate phosphors, giving a product of fine grain which may not require milling or other severe grinding (which is expensive and tends to harm emission properties) to bring it into the preferred particle size range for lamp manufacture. In this process the source of alumina is aluminium ammonium sulphate (ammonium alum) and this is mixed with oxides of the other constituent metals (or decomposable compounds thereof) and fired at temperatures above 120…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.