Peng Zhang,Wenxia Wu,Limin Wu,Yazhao Wang,Shengdi Ta,Zeyu Cheng,Shoulei Xu,Bernard Albert Goodman,Wen Deng
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. Nd3+ entered into the crystal structure during crystal growth, and the lattice parameters and cell volume increased with increasing Nd2O3 concentration as Nd3+ replaced the smaller Y3+. A series of absorption peaks involving transitions from the Nd3+ ground state (4I9/2) were observed in the UV-vis-NIR absorption spectra. Under excitation with yellow light at 589 nm, up-conversion luminescence spectra showed three distinct emission peaks, corresponding to the 4D5/2 → 4I9/2 (334 nm), 4D3/2 → 4I9/2 (363 nm) and 2P1/2 → 4I9/2 (442 nm) transitions. The maximum intensity of the emission spectra was with 0.75 mol% Nd2O3, and higher concentrations resulted in quenching through electric dipole–quadrupole interactions. From analysis of the absorption and emission spectra using the Judd–Ofelt theory, values for the strength parameters Ωt (t = 2, 4, 6) and radiative transition properties were obtained for the (ZrO2)92(Y2O3)7.25(Nd2O3)0.75 single crystal. These showed Ω4> Ω2> Ω6, with the large Ω2 value indicating a highly covalent interaction and asymmetric local environment for Nd3+. The spectroscopic quality factor (χ) and radiative properties, such as the transition probability, radiation lifetime and branching ratio, indicate that this sample is a potential material for near-UV up-conversion luminescence and laser output.
In this study, 12 mol% ceria-stabilized tetragonal zirconia polycrystal ceramics with xNd2O3(where x equals 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.7) were synthesized via the solid-state method, and the effects of Nd2O3doping amounts on the mechanical properties and microstructure were studied. The results show that with an increase in the Nd2O3doping amount, the grain size of the ceramics was reduced from 2.93 μm to 0.69 μm. The hardness and strength of the ceramics increased significantly, while the fracture toughness decreased. The reduction in fracture toughness was attributed to the reduction in tetragonal grain size, which suppressed the tetragonal–monoclinic phase transformation caused by stress. Additionally, as the content of Nd2O3increased, the formation of cubic zirconia accelerated, but no second phase was observed. Most importantly, when the doping amount of Nd2O3reached 0.3 mol%, the comprehensive mechanical characteristics of the ceramics were optimal. This provides a research basis for the preparation of nanoscale 12 mol% ceria-stabilized tetragonal zirconia polycrystal ceramics.
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