The Tb3+ activated oxyorthosilicates of the system Y2−‐xGdxSiO5 crystallize in the X2 (x ≦ 1.2) or the X1 type (x = 1.6). The CL and PL properties are strongly influenced by the crystal structure. The X1 type is more efficient in PL and the X2 structure in CL. The influence of the Gd3+ content on the CL and PL properties is studied and discussed.

Cathode ray excitation of X2–Y2SiO5:Eu3+ results in a moderate red emission. The efficiency is enhanced considerably (≈ 700%) by the simultaneous introduction of a high Tb3+ concentration (e.g. YTbSiO5:Eu3+). An enhancement of the photoluminescence emission is observed as well. The luminescence properties are studied as a function of the Tb3+ content. The mechanism of energy transfer in cathodo‐ and photoluminescence are discussed.

Cathode ray irradiation of the pure Cd garnet (x = 0) yields an intense blue emission; activation with manganese results in an intense long‐lived yellow emission due to an energy transfer from defect centres to the activator. UV excitation of Cd3Al2Ge3O12: Mn results in an yellow emission as well. In the system Cd3−xCaxAl2Ge3O12 a complete series of solid solutions is formed. For higher Ca content (x > 1) the intensity of the defect and also the Mn emission is reduced considerably. The luminescence properties are studied as a function of the Cd/Ca ratio.

The cathodoluminescence and photoluminescence properties of the strongly self‐activated pure host system Cd3‐−xCaxGa2Ge2O12 and the energy transfer between defect centres of the host and the activator Mn2+ are reported. It is demostrated that the trap structure and the transfer rate are strongly influenced by the Cd/Ca ratio and may result in an intense, long‐lived yellow Mn2+ emission for cathode ray as well as UV excitation.

The Cd garnet Cd3Al2Ge3O12 activated with Tb3+ is an efficient green emitting phosphor. Under cathode ray excitation its efficiency is about 75% of that of Y3Al5O12:Tb3+ (P 53); the corresponding value for UV excitation is about 70%. The high efficiency is ascribed to an energy transfer between defect centres of the host and the activator, considerably reduced with increasing Ca content in the series Cd3−xCaxAl2Ge3O12:Tb3+. The luminescence properties are studied as a function of the Cd/Ca ratio.