Abstract of Publication No. 470
K2NaScF6 crystals codoped with V3+
and Er3+ exhibit some novel cooperative near-IR to visible
upconversion processes at cryogenic temperatures. V3+ mainly
acts as a broadband sensitizer. The V3+
3T2g excitation between 13 500
and 15 500 cm–1, after fast relaxation to V3+
1T2g, can be transferred to
Er3+ 4I11/2, and then upconversion takes
place. Four upconversion mechanisms are identified and characterized.
For narrow-band laser excitation the overall efficiency of the
upconversion processes is low. However, at 12 K for broadband
excitation, such as in a lamp, between 12 000 and 14 500
cm–1 the number of emitted visible photons is roughly
doubled by codoping V3+ in addition to Er3+.