Abstract
Ce3+ and Tb3+ singly doped and codoped CaAl 4O7 and Y2O3 single crystal fibers were grown using the laser heated pedestal growth method. Energy transfer from Ce3+ to Tb3+ was studied in these samples. No energy transfer between Ce3+ and Tb3+ was observed in codoped Y2O3. This is because electrons excited into the Ce 3+ 5d states delocalize into the conduction band at a rate that is faster than the interionic energy transfer rate, whereas the converse is the case for CaAl4O7 doped with Ce3+ (1 at %) and Tb3+ (1 at %). The energy transfer rate was determined to be on the order of 109 's-1. The transfer occurs before the excited electrons can be thermally promoted into the conduction band. From these results, it can be inferred that the thermal ionization rate (WTh) from the lowest 5d excited Ce3+ state at 355 nm is less than 10 9 s-1 at room temperature, whereas the delocalization rate (WD) into the conduction band is faster than this rate. The location of the Tb3+ and Ce3+ states relative to the valence and conduction band of these two materials has been determined through photoconductivity measurements.
Original language | English |
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Article number | 235113 |
Pages (from-to) | 235113-1-235113-5 |
Journal | Physical Review B - Condensed Matter and Materials Physics |
Volume | 69 |
Issue number | 23 |
DOIs | |
State | Published - Jun 2004 |