Transparent single crystals of (ZrO2)92(Y2O3)8-x(Nd2O3)x ( x=0.30, 0.50, 0.75, 1.00, 1.25, 1.50) were prepared by the optical floating zone method, and shown by XRD to have a cubic phase structure....

Large-size and high-quality stable ZrO 2 single crystals containing x mol % Yb 2 O 3 (x = 7, 8, 9, 10) (denoted as xYbSZ), and 8YbSZ crystals doped with 0.5 mol % Er 2 O 3 were grown by the optical floating zone (OFZ) method. Yb 3+ was indicated by XRD and Raman spectroscopy to have successfully entered into the ZrO 2 lattice, which was stabilized in the cubic phase when the concentration of Yb 2 O 3 was ≥8 mol %. Er 3+ successfully entered the 8YbSZ lattice, and its spectral absorption intensity was enhanced compared to Er 3+ in the corresponding yttria-stabilized zirconia (8YSZ), thus demonstrating that the Yb 3+ ion has an excellent sensitizing effect on the up-conversion luminescence of Er 3+ . Fluorescence decay curves show that the up-conversion luminescence excited state lifetime of Er 3+ is significantly enhanced in 8YbSZ compared to 8YSZ. Thus, these results demonstrate that Yb 3+ ions not only successfully stabilize ZrO 2 in the cubic phase structure but also maintain their role as an up-conversion luminescence sensitizer for Er 3+ ions.

Blue, green, and red emissions through upconversion and energy transfer processes are investigated as a function of the Tm3+ concentration in Tm/Er/Yb triply doped yttria stabilized zirconia (YSZ) crystals upon excitation at 980 nm. YSZ doped with 0.075–0.250 mol% Tm2O3, 1.50 mol% Er2O3, and 2.00 mol% Yb2O3 are prepared by the optical floating zone method, and confirmed to be in the cubic phase by X‐ray diffraction. The blue emission corresponds to the Tm3+ 1G4→3H6 transition, and is produced through a three‐photon process, whereas the green and red light are emitted through two‐photon processes from the Er3+ 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions for green and the Er3+ 4F9/2→4I15/2 transition for red. However, interactions between the different lanthanide ions is a factor in determining the overall color of these triply doped crystals, and this is not simply a summation of the results from the singly doped systems, so this mechanism of energy transfer is discussed in detail. The CIE color chromaticity coordinates for the present samples under excitation at 980 nm approach (0.39, 0.55), which is in the yellow‐green region.

A series of yttria-stabilized zirconia single-crystals doped with 0.000–0.250 mol% Tb4O7 was prepared by the optical floating-zone method. As shown by XRD and Raman spectroscopy, all of the crystals had a cubic-phase structure. These were initially orange–yellow in color, which is indicative of the presence of Tb4+ ions, but they then became colorless after being annealed in a H2/Ar atmosphere as a result of the reduction of Tb4+ to Tb3+. The absorption spectra of the unannealed samples show both the 4f 8→4f 75d1 transition of Tb3+ ions and the Tb4+ charge-transfer band. In addition, the transmittance of the crystals was increased by annealing. Under irradiation with 300 nm of light, all of the single-crystal samples showed seven emission peaks in the visible region, corresponding to the decay from the 5D3,4 excited state of Tb3+ to the 7FJ (J = 6–0) states. The most intense emission was at 544 nm, which corresponds to the typical strong green emission from the 5D4→7F5 transition in Tb3+ ions.

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