Single crystals of Bi2Ge30g of optical quality with dimensions of approximately 15 x 15 x 50 mm3have been grown by the Czochralski technique from a stoichiometric melt. The space group is P 63/m, Z = 2, at = 0.7006 nm, a3 = 0.9786 nm. The structure (R = 0.052) is closely related to that of benitoite. Trigermanate rings are located in planes perpendicular to the six-fold axis. The elastic and thermoelastic constants, the indices of refraction, and the coefficients of thermal expansion have been measured. The elastic properties reveal strong covalent bonds which are assigned to the trigermanate rings. Thermal expansion parallel to the six-fold axis is extremely small. The crystals are potentially feasible for X-ray spectrometer applications and photoacoustic deflector devices.

The afterglow properties of (Y,Gd)2O3:Eu ceramics and related defects formed by X-ray irradiation have been investigated. Temperature-dependent afterglow measurements have been compared with thermoluminescence curves and it has been found that afterglow of (Y,Gd)2O3:Eu is caused by thermally unstable trapped charge carriers. Codoping of Pr results in a strong decrease of afterglow. During X-ray irradiation Pr4+ is formed, which has been identified by comparing absorption spectra of X-ray irradiated and oxidized samples. Thermoluminescence measurements of (Y,Gd)2O3:Eu,Pr show that Pr3+ acts as an effective hole trap which successfully competes with the intrinsic hole traps and is found to be stable up to 700 K. The thermally unstable intrinsic hole traps which are responsible for the high afterglow at room temperature are no longer occupied and therefore afterglow is drastically reduced.

The luminescence of Pr3+ in gadolinium sulfate hydrate is reported for 195 nm laser excitation. The Pr3+ ion acts as a sensitizer of the host lattice emission. The pr(3+) --> Gd3+ energy transfer occurs in two different ways. In the octahydrate the transfer occurs from the lowest component of the 4f5d configuration of Pr3+, but in the samples with less water there is energy transfer from the S-1(0) level of Pr3+ to several Gd3+ levels. The Pr3+ emission in the two modifications is, of course, also strikingly different.

Gadolinium gallium garnet ceramics (GGG) doped with CP3+, Pr3+ and Bi3+ have efficient luminescence. Excited by X-rays some of the investigated scintillators show an afterglow which is detrimental to an application in medical radio diagnostics. Thermoluminescent measurements between 50 K and 600 K gave results that allow to estimate the trap concentration in these materials. Only shallow traps could be found in GGG:Cr. It seems that these traps are caused by lattice defects relative to oxygen deficiency. The thermoluminescence at higher temperatures of GGG:Pr and GGG:Bi reveals deep traps which determine the afterglow in these luminescent materials.

The luminescence of Pr3+ in gadolinium sulfate hydrate is reported for 195 nm laser excitation. the Pr3+ ion acts as a sensitizer of the host lattice emission. The Pr3+→Gd3+ energy transfer occurs in two different ways. In the octahydrate the transfer occurs from the lowest component of the 4f5d configuration of Pr3+, but in the samples with less water there is energy transfer from the1So level of Pr3+ to several Gd3+ levels. The Pr3+ emission in the two modifications is, of course, also strikingly different.

The luminescence of Bi3+ in the garnet structure is described for the first time. It consists of a broad emission band with a maximum at 480 nm. There is a strong analogy with La2O3:Bi. Time-resolved spectra are also reported. They yield information on the feeding process of the luminescent centers in the gallate garnet.

Luminescence properties of Pr3+-doped C-type sesquioxides Ln2O3 (Ln = Sc, Y, Gd) have been investigated. In cubic Ln2O3, the rare earth ion Pr3+ occupies two different cation sites with site symmetry C2 and S6. For all three sesquioxides, pairs of two distinct emission and excitation spectra were recorded. Time-resolved spectroscopy was used to assign the spectra to the two cation sites. In both emission spectra of site C2 and site S6, only the electric dipole transition 1D2 → 3H4 of Pr3+ was observed. The spectrosc results were correlated with structural data to clarify the luminescence mechanism in cubic rare earth oxides

The preparation of GdVO4:Bi3+ ceramics is indicated. Bismuth shows a strong tendency to evaporate during the sintering process. Time-resolved emission spectroscopy shows for sufficiently low Bi3+ concentrations subsequently: blue VO 4 3− emission with a decay time corresponding to the transfer rate (106 s−1), yellow VO 4 3− −Bi3+ emission, rare-earth impurity emission and VO 4 3− −Bi3+ afterglow.