EVIDENCE OF EU3-O2- ASSOCIATES BY LUMINESCENCE STUDY OF SOME SILICATES AND ALUMINOSILICATES()

Unusual luminescence spectra with a strong D-5(0) --> F-7(0) line, a h igh position of the D-5(0) level and the occurrence of two lines close to 16550 cm(-1), i.e. in a frequency domain at the border between D-5 (0) --> F-7(2) and D-5(0) --> F-7(1) transitions, have been evidenced in the case of cordierite, Mg2Al4Si5O18:Eu, mullite, 2Al(2)O(3)SiO(2): Eu and lanthanum disilicate, La2Si2O7:Eu. By comparison with results o n apatites and some fluorides, these unusual spectra have been attribu ted to the presence of a strong and anisotropic crystal field due to a n Eu-O bonding. (C) 1997 Elsevier Science S.A.