LUMINESCENCE OF THE EU3+ ION IN ZR4+ COMPOUNDS

The luminescence of the Eu3+ ion in some Zr4+ compounds is reported in order to study the influence of the effectively negative charge of the Eu3+ ion on the quantum efficiency for charge-transfer excitation. This effectively negative charge of the Eu3+ ion does not in principle enhance radiationless relaxation rates in the excited charge-transfer state, but the presence of vacancies in the structure may lower the efficiency considerably. For the Eu3+ luminescence in ZrO2 and ZrP2O7 the quantum efficiencies amount to about 30% and 60%, respectively. In these compounds the presence of vacancies may account for these values. In Li2ZrO3:Eu3+ with a relatively low Li+ concentration it seems as though the partial incorporation of the Eu3+ ions on a Li+ site accounts for the low efficiency (about 10% at room temperature). The incorporation of the Mg2+ ion as a charge compensator in the Li2ZrO3 lattice increases the quantum efficiency up to at least 60%.