Luminescence properties of Eu2O3-doped ZrO2–Y2O3 single crystals

Abstract

The synthesis, structure, and optical properties are reported for a series of yttria-stabilized zirconia crystals in which some Y³⁺ was replaced by Eu³⁺. These crystals were grown by the optical floating zone (OFZ) method and were transparent without inclusions, cracks, or bubbles. They were all exclusively in the cubic phase, whereas the corresponding ceramic samples had a mixture of monoclinic and cubic phases. Absorption spectra showed a charge transfer band at 268 nm and a series of narrow peaks in the range 308–540 nm from Eu³⁺ f–f transitions. The crystals were efficiently excited at 393 nm, and exhibited excellent orange-red photoluminescence (PL) centred at 610 nm, from the ⁵D₀ → ⁷F₁ transition. The maximum PL intensity was observed with crystals prepared with 2.00 mol% Eu₂O₃, and compared with other rare earth ions; Eu³⁺-doped ZrO₂–Y₂O₃ single crystals have a high concentration quenching threshold. The critical distance for Eu³⁺ ions was calculated as 11.8 Å, which indicates that multipole–multipole interactions dominate the non-radiative energy transfer between Eu³⁺ ions. Finally, the chromaticity coordinates (CIE) for all the samples were similar, and those for the (ZrO₂)₉₂(Y₂O₃)₆(Eu₂O₃)₂ crystal were (x = 0.6339, y = 0.3657) with a colour purity >98%.