The compositions
MIIM2IIIfalse(S,normalSe)4 normalwhere MII=normalEu,,normalCa,normalSr,normalBa and MIII=normalAl,normalGa
, In were prepared by reaction of the elements in evacuated silica tubes with iodine as a mineralizer. All members except
normalBafalse(normalGa,normalAl)2S4
, which is cubic, exhibit the pseudo‐orthorhombic
PbGa2Se4
type structure. They are high resistivity p‐type semiconductors; they exhibit Eu+2‐activated fluorescence which varies from red to blue as the electropositive character of the cations increase. Fluorescence activated by Yb+2 is seen at low temperature. Studies were made of the fluorescence decay lifetimes, temperature dependence, excitation spectra, and optical adsorption of
SrGa2S4
: Eu in order to relate the Eu+2‐activated fluorescence to the host bandgap. It is concluded that the most efficient phosphors are those in which the Eu+2 excited states lie farthest from the fundamental edge.
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