Photoluminescence of Y2.3−xTbxCe0.05Gd0.65Al5O12
(x = 0.575,
1.15, 1.725 and 2.3) has been measured at room temperature at high hydrostatic
pressure. Under excitation at 457 nm, the broad band emission related to
interconfigurational transition from the lowest state of excited electronic configurations
5d1
to the ground state split by spin–orbit interaction into
2F5/2 and
2F7/2 components
of Ce3+
ions, peaked at 550 nm, is seen. Under excitation with 325 nm one observes mainly the
sharp luminescence lines related to , , and transitions in Tb3+
ions. One observes a strong pressure induced red-shift of the
Ce3+ emission approximately
equal to −20 cm−1 kbar−1 and much smaller
shifts (approximately −1 cm−1 kbar−1) of the energies of the sharp lines related to
Tb3+
luminescence. It has been found that the efficiency of energy transfer depends on Tb content and excitation energy; specifically, it is less effective when
Tb3+ is excited to the lowest
state of the excited 5d14f7
electronic configuration. This effect has been tentatively attributed to the nonradiative de-excitation of the
Tb3+ ion to the
metastable 5D4
state. A configurational model has been developed, which explains peculiarities of relaxation in the excited
states of Tb3+
and energy transfer.
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