EU-2+ LUMINESCENCE IN MAL3BO7 ALUMINOBORATES (M=CA,SR,BA)

Three new aluminoborates having the composition MAl3BO7, where M = Ca,Sr or Ba, have been prepared. X-ray diffraction data indicate that all the phases are monoclinic, with close structural similarity to the meta stable aluminate, SrAl4O7. These aluminoborates are good host lattices for Eu2+ luminescence. The emission spectra show multiple bands in the blue region, corresponding to two inequivalent sites in each case, with one of them having quantum efficiency greater than or similar to 75%. In the case of SrAl3BO7:Eu2+, the d-f band emission dominates at 300 K whereas at 77 K both d-f band and f-f line emissions are observed. Efficient Eu2+ --> Mn2+ energy transfer is observed in MAl3BO7 leading to strong green emission of Mn2+ in the tetrahedral sites.