Luminescence and site occupancy ofCe3+inBa2Ca(BO3)2

The phosphors of ${\mathrm{Ce}}^{3+}$ activated ${\mathrm{Ba}}_{2}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ with chemical formulas ${\mathrm{Ba}}_{2(1\ensuremath{-}x)}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ and ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}2x}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ were prepared. The luminescence properties have been investigated under vacuum ultraviolet UV and x-ray excitation. Though the point defects ${\mathrm{Ce}}_{{\mathrm{Ba}}^{\mathbf{∙}}}$ and ${\mathrm{Na}}_{{\mathrm{Ba}}^{\ensuremath{'}}}$ are expected to occur in samples ${\mathrm{Ba}}_{2(1\ensuremath{-}x)}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$, and ${\mathrm{Ce}}_{{\mathrm{Ca}}^{\mathbf{∙}}}$ and ${\mathrm{Na}}_{{\mathrm{Ca}}^{\ensuremath{'}}}$ are expected to appear in samples ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}2x}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ according to the formulas of the compounds, however, two types of ${\mathrm{Ce}}^{3+}$ centers were found in all samples due to the occupancy of both ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Ca}}^{2+}$ sites. So the influence of doping concentration on the preferential site occupancy was studied, and it was found that ${\mathrm{Ce}}^{3+}$ ions always preferentially enter ${\mathrm{Ba}}^{2+}$ sites at low doping concentration for both samples ${\mathrm{Ba}}_{2(1\ensuremath{-}x)}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ and ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}2x}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$. In addition, the $5d$ energy levels and decay behaviors for ${\mathrm{Ce}}^{3+}$ in ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Ca}}^{2+}$ sites, the concentration quenching, and the x-ray excited photon output were evaluated to clearly reveal the luminescence features.