Strength and crack resistance of zirconium dioxide crystals containing yttrium and terbium oxides

Conclusions We studied the mechanical behavior of the partially stabilized (with yttrium oxide) zirconium dioxide crystals in which a small quantity of terbium oxide was introduced as an additive. The obtained data indicate the suitability of this material for practical applications. The effect of heat treatment on the physical and mechanical properties of such materials was revealed. It was established that on cooling up to –150°C, their strength and thermal shock resistance are improved.The lack of correspondence between the values of the crack resistance determined according to the methods of bend testing and indentation was established. The existence of a significant barrier to fracture was observed. The two possible types of surfaces of the crystals under consideration were revealed and the relationship between the structure of these surfaces (and, also, the near-surface layers adjoining them) and the resistance to fracture was established.Translated from Ogneupory, No. 6, pp. 2–8, June, 1993.     

Structure and conductivity of yttria and scandia‐doped zirconia crystals grown by skull melting

In this paper a detailed study of the (ZrO₂)_1‐x(Y₂O₃)_x (x=0.025–0.15), (ZrO₂)_1‐x(Sc₂O₃)_x (x = 0.06 – 0.11) and (ZrO₂)_1‐x‐y(Sc₂O₃)_x(Y₂O₃)_y (x=0.07 – 0.11; y=0.01 – 0.04) solid solution crystals grown by skull melting technique is presented. The structure, phase composition, and ion conductivity of the obtained crystals were investigated by X‐ray diffraction, transmission electron microscopy, Raman scattering spectroscopy, and impedance spectroscopy. Maximum conductivity as (ZrO₂)_1‐x(Y₂O₃)_x and (ZrO₂)_1‐x(Sc₂O₃)_x solid solution crystals is observed for the compositions containing 10 mol% stabilizing oxide, and the conductivity of 10ScSZ is ~3 times higher than for 10YSZ. Experiments on crystal growth (ZrO₂)_1‐x‐y(Sc₂O₃)_x(Y₂O₃)_y solid solutions showed that uniform, transparent crystals 7Sc3YSZ, 7Sc4YSZ, 8Sc2YSZ, 8Sc3YSZ, 9Sc2YSZ, 9Sc3YSZ, 10Sc1YSZ, and 10Sc2YSZ are single phase crystal containing t″ phase. It is established that a necessary condition of melt growth of (ZrO₂)_1‐x‐y(Sc₂O₃)_x(Y₂O₃)_y single‐phase crystals is the total concentration of the stabilizing oxides from 10 to 12 mol%. The addition of Y₂O₃ affects the (ZrO₂)_1‐x‐y(Sc₂O₃)_x(Y₂O₃)_y solid solution conductivity different ways and depends on the Sc₂O₃ content in the starting composition. The effects of structure, phase composition, concentration, and type of stabilizing oxides on the electrical characteristics of obtained crystals are discussed.     

Change in the mechanism of conductivity in ZrO<Subscript>2</Subscript>-based crystals depending on the content of stabilizing Y<Subscript>2</Subscript>O<Subscript>3</Subscript> additive

The interrelationship between the structure, phase composition, and transport characteristics of solid electrolytes based on ZrO₂ has been studied as dependent on the content of stabilizing Y₂O₃ additive. It is established that twin boundaries do not lead to the appearance of additional mechanism of ionic conductivity acceleration in ZrO₂–Y₂O₃ crystals. The maximum conductivity has been observed in ZrO₂–(8–10) mol % Y₂O₃ crystals containing a t” phase, in which oxygen atoms are displaced from high-symmetry positions characteristic of the cubic phase.     

Effect of Y<Subscript>2</Subscript>O<Subscript>3</Subscript> stabilizer content and annealing on the structural transformations of ZrO<Subscript>2</Subscript>

The structure of partially stabilized zirconia crystals has been studied by transmission electron microscopy before and after annealing. Structural characterization of Y₂O₃-doped (2.8 to 4 mol %) zirconia before annealing showed that all of the samples consisted of twin domains whose size was dependent on the stabilizer content. Annealing at 2100°C increased the domain size in the composition range 2.8–3.7 mol % Y₂O₃ and reduced it at 4 mol % Y₂O₃. These structural changes allowed us to determine the position of the representative point relative to the phase boundary in the equilibrium phase diagram of the system.     

Zirconia crystals with yttrium and cerium oxides

Results obtained for a new material, namely, zirconia crystals stabilized by Y₂O₃ and CeO₂ and containing a technological addition of neodymium oxide, tested at room temperature are described. Special features of the surfaces of the crystal blocks grown and the distribution of the additions introduced into the charge over their height are investigated. The dependences of the amounts of the stabilizing components and the fracture properties of the investigated material on its strength are determined. Certification results for the mechanical characteristics of the material are presented (mean four-point bending strength 1250 MPa, crack resistance in bending of a notched bar 11.43 MPa·m^1/2 at an elasticity modulus of 366 GPa for the crystallographic direction 100). The crystals are investigated in the crystallographic plane {100} by applying Vickers and Knoop indenters, and their hardness at different loads (beginning with 0.1 N) is determined. It is established that zones of phase transformations are formed near the indentations in addition to radial and lateral cracks. Problems of change in the specific features of the mechanical behavior of the crystals with change in the valence of cerium (most experiments were conducted for Ce₂O₃), with the heat treatment, etc. are considered. The results are analyzed using data of fractographic investigations and the new data obtained in tests of similar crystals partially stabilized by yttrium and terbium oxides.Translated from Ogneupory, No. 7, pp. 2–10, July, 1995.     

Effect of the Phase Composition and Local Crystal Structure on the Transport Properties of the ZrO2–Y2O3 and ZrO2–Gd2O3 Solid Solutions

Russian Microelectronics - The results of investigating the crystal structure, ionic conductivity, and local structure of the (ZrO2)1 –x(Gd2O3)x and (ZrO2)1 –x(Y2O3)x (x = 0.04, 0.08,...     

Preparation and properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript> partially stabilized ZrO<Subscript>2</Subscript> crystals

We have studied the effect of composition and growth conditions on the structure and properties of 2.5–5 mol % Y₂O₃ partially stabilized ZrO₂ crystals grown by directional solidification in a cold-wall crucible. The phase composition and density of the crystals have been determined. The crystals are shown to be uniform in composition, with local changes in Y₂O₃ content within ±0.5 mol %. The dimensions and quality of the single crystals are influenced by the growth conditions.     

Features of a technique for investigation of partially stabilized zirconia crystals

The structure of partially stabilized zirconia crystals is investigated by X-ray diffractometry and transmission electron microscopy. It is shown that the combination of structural methods allowed one to reveal features of the structure and phase composition of these materials. Partially stabilized zirconia has a complex twin-domain structure. X-ray diffractometry with the use of K _β radiation shows the presence of two phases of the tetragonal modification of zirconia with different tetragonality in all investigated samples independently of the content of the stabilizing impurity. The combination of the locality of transmission microscopy with the integral nature of X-ray diffractometry allowed one to reveal the dependence of the dispersion of twin domains on the concentration of the stabilizing impurity. The use of transmission microscopy with high resolution demonstrates the hierarchy of twinning and the presence of twin domains ～10 nm in width.