So far, most of the studies on GaN doped with beryllium have mainly concentrated on possible p-type doping. Unfortunately, realization of p-type conductivity in such a way appeared to be very difficult. It seems, however, that bulk crystals doped with beryllium can be used as white light converters in the monolithic white light emitting diodes. To realize monolithic white light emitting diode, we used blue light emitting diodes and a single GaN:Be crystal as converter. High value of the Color Rendering Index gives hope for obtaining an effective light converter based on gallium nitride doped with beryllium.

This study is focused on obtaining large CeAlO3 single crystals. Using Czochralski and Edge-Defined Film Fed Growth techniques, crystals of length up to 130 mm were obtained. The crystals belong to the tetragonal low temperature modification of CeAlO3, space group P4/mmm, a=3.7669Å, с=3.7967Å. Density and crystallographic parameters, as well as some optical, luminescence and magnetic properties of CeAlO3 were studied. The crystals demonstrate rather bright luminescence under UV-excitation, while no luminescence has been registered under Xrays. Ceramic and single crystalline CeAlO3 samples demonstrate p-type conductivity and promising paramagnetic properties.

The work presents experimental results of an in situ investigation of optical absorption of LiNbO(3) : MgO during reducing (95%Ar + 5%H(2)) and oxidizing (O(2)) high-temperature treatments in the temperature range from room temperature to 1073 K. The absorption spectra measured at in situ conditions at high temperatures in reducing/oxidizing atmospheres as well as the kinetics recorded at fixed wavelengths during rapid replacement of gas atmospheres have been analyzed. The origin of the changes in optical absorption caused by the reducing/oxidizing treatments is discussed in terms of hydrogen and oxygen ion diffusion and the point defect structure of the material.

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