S. Yu. Pliner

Strengthening ceramic materials due to phase inversion of ZrO2 (Review)

Mecanisme de la transformation de phase martensitique des particules de ZrO 2 . Mecanisme du renforcement du a la microfissuration. Cas des systemes alumine-zircone, mullite-zircone, forsterite-zircone, ZrO 2 cubique-ZrO 2 quadratique, Si 3 N 4 -ZrO 2

High-strength ceramic from zirconium dioxide partly stabilized with ytterbium oxide

ConclusionsIn the Yb2O3-ZrO2 system it is possible to obtain high-strength ceramic by using the method of low-temperature sintering of active ZrO2 powders with concentrations of 3.0–3.5% Yb2O3. The factors determining the strength of the ceramic are the size of the grains and the concentration of tetragonal phase.

Properties of the partially stabilized zirconium dioxide crystals

Etude des proprietes physicomecaniques des cristaux de zircone stabilisee par 5 a 6% en poids de Y 2 O 3

Increasing the strength of ceramics made of zirconium dioxide due to eutectoid decompostion of solid solutions in the system ZrO2-MgO

The aim of this work was to study the influence of the amount of MgO and the firing schedule on the strength of the ceramics, and also to evaluate the possibility in principle of using ceramics made from solid solutions of MgO in ZrO/sub 2/ for preparing various design parts, since the use of tetragonal solid solutions of Y/sub 2/O/sub 3/ in ZrO/sub 2/ for these purposes, despite the obvious technical advantages, is economically undesirable due to the high cost of the yttrium oxide.

High-strength ceramic made from tetragonal zirconia with additions of alumina

The aim of this investigation was to study the possibility of preparing high-strength ceramic from tetragonal ZrO/sub 2/ containing additions of Al/sub 2/O/sub 3/ by mixing powders in water suspensions. The prepared and stabilized suspensions of powdered ..cap alpha..-Al/sub 2/O/sub 3/ and ZrO/sub 2/ with an addition of 5% Y/sub 2/O/sub 3/ were mixed in a rotating polyethylene drum. The specimens were obtained by casting in gypsum molds, and fired in air in an electric furnace at 1400-1550/sup 0/C. The measurements of the bending strength were made by the three-point technique at 20/sup 0/C according to GOST 5458-75 on ground specimens measuring 4 x 5 x 50 mm, and for the x-ray analysis they used the DRON1-UM diffractometer. The relative density of the ceramic was assessed with respect to the apparent density and the density of the monocrystals of tetragonal ZrO/sub 2/ (6.12 g/cm/sup 3/) and of corundum (3.99 g/cm/sup 3/); the open porosity was determined according to GOST 2409-67. The results are shown.

Influence of grain size on the strength of ceramics made from hafnium dioxide partly stabilized with yttrium oxide

ConclusionsThe strength of fine-grained ceramics made from hafnium oxide with an addition of 3–5% Y2O3 largely depends on the size of the component grains. Ceramic with a grain size of about 1 μm containing 4% Y2O3 has a bending strength of about 480 N/mm2, which is twice as high as for ceramics made of cubic HfO2.

The temperature field of oxide material heating elements

This paper presents a theoretical formulation for the temperature-dependent electric conductivity of refractory oxides used as heating elements inelectric furnaces. The formulation calculates the temperature distribution and optimizes the thermal efficiency of the oxide based on thickness and configuration and thermal conductivity of the material. Zirconium dioxide is used to demonstrate the reliability and accuracy of the theoretical procedure. Hafnium and thorium oxides are listed as candidate materials to which the formulation can also be applied successfully.

High-strength ceramics from tetragonal zirconium dioxide

ConclusionsUsing as an example solid solutions of Y2O3 in ZrO2 we demonstrated the possibility of obtaining ceramics from tetragonal ZrO2 containing 3.5% Y2O3 possessing high mechanical properties up to temperatures of 700°C.

Effect of the concentration of anion vacancies and the radius and charge on the cation of the stabilizing oxide on the conductivity of solid solutions based on ZrO2

ConclusionsAn increase to 4.5–5.5% in the concentration of anion vacancies in the lattice facilitates the transport processes in solid solutions. With a significant concentration of anion vacancies this process becomes difficult, as is indicated by the increase in the activation energy of conductivity.The stabilization of ZrO2 by oxides with a larger cation radius leads to a reduction in the level of conductivity of the solid solutions.The addition to the ZrO2 lattice of cations of stabilizing oxides with a charge close to that of Zr4+ facilitates the transport process of the oxygen ions.It is shown that, in principle, it is possible to predict the level of conductivity of solid solutions based on ZrO2 at 1200–1400°C.The use of a combined additive consisting of a mixture of rare-earth oxides to stabilize ZrO2 makes it possible to obtain solid electrolytes close in their electrophysical properties to the ZrO2-Sc2O3 electrolytes.

Obtaining strong zirconia ceramic by hardening and tempering

ConclusionsUsing a solid solution of 3.4% Y2O3 (molar fraction) in ZrO2 we demonstrated that it is possible to strengthen ceramics on account of the monoclinic-tetragonal conversion of ZrO2 with the use of specific heat-treatment cycles (hardening and tempering).