Spectrally resolved microprobe cathodoluminescence of intergrowth Bi5-xLaxTiNbWO15 ferroelectrics

Spectrally resolved cathodoluminescence measurements of Bi5-xLaxTiNbWO15 (x=0-1.50) ceramics at room temperature showed three distinct luminescence bands located at about 380, 502, and 660 nm, respectively, which were tentatively assigned to F+ center, oxygen vacancy-related defect and octahedron structure-related luminescence center, respectively. These assignments could be made in light of electron irradiation experiments with different exposure times. Bands related to oxygen vacancies were clearly enhanced by lanthanum doping, indicating that charge compensation occurred by the substitution of Bi for La3+ in perovskitelike structured intergrowth ferroelectrics. We observed that, for contents of La3+ x>0.75, La3+ ions entered the [Bi2O2](2+) layer according to a doping mechanism which is briefly discussed in this letter. (C) 2007 American Institute of Physics.