Improvement of green emission from Tb~(3+):GdOBr phosphors by Ce~(3+) co-doping

摘要

A strong green emission (~5D_4→~7F_5) has been observed from Tb~(3+) (1mol%) doped GdOBr powder phosphors upon excitation with an UV-wavelength (226nm). To such a bright green color display phosphor material, different amount of Ce~(3+) from 0.1 to lmol% has been added to further improvise the green emission efficiency. It has been found that 0.2mol% of Ce~(3+) is the optimum content which resulted in an enhancement in the green emission intensity by five or six times compared to that of the singly doped terbium phosphors. It has been noted that with the increment of Ce~(3+) concentration, green emission of Tb~(3+) could not increased due to the strengthening of Ce~(3+)-Ce~(3+) ion interaction or the concentration quenching effect. The mechanism involved in the energy transfer between the Ce~(3+) and Tb~(3+) has been explained using the energy level diagram. Energy absorbed by the sensitized Ce~(3+) ions could be transferred to fluorescent Tb~(3+) ions by means of resonant energy transfer and this is mainly due to dipole interaction.