Growth and optical properties of thulia-doped cubic yttria stabilized zirconia single crystals

Single crystals of yttria stabilized zirconia (YSZ) doped with different thulia (Tm 2 O 3 ) contents (0.2–3.0 mol%) (abbreviated to Tm 2 O 3 : YSZ) were grown by the optical floating zone method. The crystals were transparent and inclusion free. These samples were then analyzed by X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DSC), and Raman spectroscopy , and their optical properties were determined with Ultraviolet–visible (UV–Vis) and Photoluminescence spectroscopy (PL). The Tm 2 O 3 : YSZ single crystals were in the cubic phase, and the lattice parameters first increased and then decreased with increasing Tm 2 O 3 content. The absorption spectra showed four peaks at around 356 nm ( 3 H 6 → 1 D 2 ), 460.5 nm ( 3 H 6 → 1 G 4 ), 678.5 nm ( 3 H 6 → 3 F 2,3 ) and 784 nm ( 3 H 6 → 3 H 4 ) in the visible region, and the optical bandgap energy increased with increasing Tm 2 O 3 content, as a result of the Moss-Burstein effect. Measurements of PL spectra indicated a strong blue emission peak at 458 nm ( 1 D 2 → 3 F 4 ), and three weak emission peaks at 487 nm ( 1 G 4 → 3 H 6 ), 497 nm ( 1 D 2 → 3 H 5 ), and 656.5 nm ( 1 G 4 → 3 F 4 ) when the crystals were excited by light with a wavelength of 356 nm. The intensities of the emission peaks were strongly affected by the Tm 2 O 3 content of the YSZ single crystals; the intensity increased with Tm 2 O 3 content at low doping levels, reached the maximum at 0.5 mol% Tm 2 O 3 , then decreased with further increase in Tm 2 O 3 content due to the concentration quenching effect. Additionally, the color changed from blue to cyan as the Tm 2 O 3 content was increased. Overall, this work demonstrates that the cubic YSZ single crystal is a suitable host material for solid state luminescence.