LUMINESCENCE SPECTRA OF PURE AND DOPED GABO3 AND LIGAO2

The luminescences of GaBO3 and LiGaO2 are reported. The former has Ga(III) in octahedral sites (calcite structure), the latter in tetrahedral sites (ordered wurtzite structure). The Ga(III) co-ordination number has the same influence on the luminescence as in the case of oxo-d0 complexes: the lower the co-ordination number, the higher the energy of the first absorption band, the larger the Stokes shift, and the less mobile the excited state. The broad-band spectra with large Stokes shift indicate that the nature of the optical transition involved is complicated. Dopants in GaBO3 are Eu(III) and Cr(III). They are characterized by magnetic-dipole emission due to the inversion symmetry site in calcite. The Cr(III) ion yields 2E emission at 4.2 K, in contrast to Cr(III) in isomorphous ScBO3 where it yields 4T2 emission. The dopant in LiGaO2 is Fe(III) which yields an intense deep-red emission with pronounced vibrational structure.