Equilibria and Eu2+ Luminescence of Subsolidus Phases Bounded by Ba[sub 3]MgSi[sub 2]O[sub 8], Sr[sub 3]MgSi[sub 2]O[sub 8], and Ca[sub 3]MgSi[sub 2]O[sub 8]

The incorporation of divalent europium in the compounds , , and produces phosphors of high luminescence yield. These phosphors respond well to both long and short wavelength ultraviolet excitation, as well as to cathode ray bombardment. The peak of the emission band occurs at progressively shorter wavelength and narrows as the radius of the major alkaline earth ion (Ca, Sr, or Ba) is increased. A 1200°C isotherm on compositions intermediate to and shows a complete series of crystalline solutions to exist at this temperature. Using an orthorhombic cell the d‐spacings of the (222) reflection vary continuously from 1.956Aå for for . The emission spectra of these samples, however, vary in a discontinuous manner. Complete crystalline solution is likewise observed in a 1200°C isotherm for compositions intermediate to and . Here the d‐spacings of the (222) reflection from the orthorhombic cell vary continuously from 1.909Aå for to 1.956Aå for . Again the peak of the emission spectra varies discontinuously with composition even for the complete crystalline solution series. Emission spectra and x‐ray diffraction data collected on samples prepared in the 1200°C subsolidus isotherm intermediate in composition to and show an intermediate compound to be formed. This compound has luminescent properties which more closely resemble those of the calcium end‐member. Several compositions were prepared in the subsolidus, 1200°C, isothermal, ternary section bounded by , , and . The samples prepared show the major feature of the section to be a large single phase region. In general, broadening of spectral energy distributions is observed as compositions move into the ternary section. All the compositions prepared resulted in phosphors of relatively high efficiency.