ZrO2–Sc2O3 Solid Electrolytes Doped with Yb2O3 or Y2O3

Russian Journal of Electrochemistry - The effects of the Y2O3 and Yb2O3 co-doping impurities on the transport characteristics and stabilization of the cubic phase in solid solutions based on...     

Structure and phase composition studies of partially stabilized zirconia

Zirconia single crystals doped with 2.8, 3.2, 3.7, and 4.0 mol % of Y₂O₃ have been studied. The phase composition and structure have been studied by X-ray diffraction analysis and transmission electron microscopy. It has been established that all investigated samples has two ZrO₂ tetragonal phases with tetragonality c/a = 1.006–1.007 and c/a = 1.014–1.015 independent of the stabilizing impurity content. The former phase is not transformed, whereas the latter is transformed into a monoclinic one. In all cases the samples have a developed twin structure. Twinning hierarchy is observed: there are first-, second-, third-order, etc., twins, each of them containing the next-order twins inside them. Elastic stress relaxation occurs by twinning rather than by generation of dislocations. The stabilizing impurity content affects the structure nonmonotonically; the minimum dimensions of the twin lamellas refer to the Y₂O₃ concentration of 3.2 mol %.     

Effect of Heat Treatment on the Thermal Conductivity of Single Crystals of ZrO2-Based Solid Solutions Stabilized with Scandium and Yttrium Oxides

Physics of the Solid State - The effect of heat treatment at 1000°C for 400 h on the thermal conductivity of zirconium dioxide crystals stabilized with scandium oxide...     

Specific Features of the Local Structure and Transport Properties of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 Crystals

Optics and Spectroscopy - The specific features of the local structure of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 crystals are revealed by optical spectroscopy using the Eu3+...     

Spectroscopy of optical centers of Eu<Superscript>3+</Superscript> ions in partially stabilized and stabilized zirconium crystals

The structure of the optical centers of Eu³⁺ ions in tetragonal (ZrO₂)_1–x–y (Y₂O₃) _x (Eu₂O₃) _y (х = 2.7–3.6; y = 0.1) and cubic (ZrO₂)_1–x–y (Y₂O₃) _x (Eu₂O₃) _y (х = 8–38; y = 0.1–0.5) crystals of solid solutions on the basis of zirconium dioxide is studied using the methods of optical and Raman-scattering spectroscopy. Characteristic optical centers of Eu³⁺ ions with different crystalline environments are revealed in the above compounds.     

Growth and analysis of barium-sodium niobate crystals

The conditions of growth, monodomenization, and detwinning are considered in order to obtain optically perfect barium–sodium niobate crystals (BSN). Optical homogeneity and that of chemical composition are investigated. It is shown that possible variations of composition in a crystal's volume are below 1%. Thermal E and optical E_g° widths of the forbidden zone are determined in the absorption spectra.     

Structure and Transport Properties of Zirconia-Based Solid Solution Crystals Co-Doped with Scandium and Cerium Oxides

The crystals of (ZrO₂)_1–x(Sc₂O₃) _x (СeO₂)_0.01 solid solutions (x = 0.08–0.10) were obtained by directional crystallization. The crystals of the grown composites were semitransparent, opalescent, and without cracks and had varying microstructure in the bulk. In the range of compositions under study, it was impossible to obtain optically homogeneous, fully transparent crystals. The crystals grown at a growth rate of 10 mm/h had a nonuniform distribution of ceria along the length of the ingot. The introduction of ceria in an amount of 1 mol % increased the conductivity of the crystals, but the increase in the specific electric conductivity depended on the Sc₂O₃ content and the phase composition of the crystals. The highest conductivity was inherent in the (ZrO₂)_0.89(Sc₂O₃)_0.10(CeO₂)_0.01 crystals.     

Study of the structural and physicochemical properties of nanostructured zirconia crystals for fabricating an innovative electrosurgical tool

To optimize the chemical composition of the crystals of nanostructured partially stabilized zirconium dioxide for fabricating cutting parts of an electrosurgical tool, the structural and strength properties of these crystals were investigated in dependence on the stabilizing impurity (Y₂O₃) content and the effect of additional dopants on the critical properties of the material was studied. It was established that in all the investigated crystals without additional doping, regardless of the stabilizing impurity content, there are two phases of zirconium dioxide tetragonal modification with different tetragonality factors, c/a = 1.006–1.007 and 1.014–1.015, the first being nontransformable and the second being transformable to a monoclinic phase. All the synthesized crystals are characterized by a pronounced twin domain structure, which forms upon cooling the single crystal during the transition of the cubic structure to the tetragonal one. It was established that the Y₂O₃ concentration in the range from 2.5 to 3.0 mol % is optimal for ensuring high values of the strength characteristics and fracture toughness of the material. Doping of the crystals with the rare-earth elements notice-ably affects their strength characteristics. One of the most promising materials for fabricating cutting blades of the electrosurgical tool is the crystals of partially stabilized zirconium dioxide doped with Ce₂O₃+Nd₂O₃, which are characterized by high fracture toughness and enhanced bending strength.     

Thermal conductivity of single-crystal ZrO2-Y2O3 solid solutions in the temperature range 50–300 K

The thermal conductivity of ZrO_2−x Y₂O₃ single crystals (x = 0.5, 1.5, 2.0, 2.5, 3.0, 8.0 mol %) has been studied experimentally in the temperature range 50–300 K. The influence of high-temperature annealings on the thermal conductivity has been analyzed.     

Structure and mechanical properties of crystals of partially stabilized zirconia after thermal treatment

The phase composition and morphology of the twin structure of the Y₂O₃-stabilized zirconia crystals (from 2.8 to 4.0 mol %) after the thermal treatment at 1600°C have been investigated by X-ray diffractometry and transmission electron microscopy. It is shown that as the concentration of the stabilizing Y₂O₃ impurity increases, the character of the twin structure changes, and the amount of the untransformed phase t′ increases. The dependence of the hardness and crack resistance of the crystals of partially stabilized zirconia on the Y₂O₃ concentration and the indenter orientation is investigated using the microindentation method. The sample with the lowest concentration of the stabilizing Y₂O₃ impurity turned out the most crack resistant. This can be explained by a high content of tetragonal phase t in it, which provides the transformation strengthening mechanism of the material, and by a more multilevel character of twinning.