Influence of precursor dispersity and agglomeration on mechanical characteristics of 92ZrO(2)-8Y(2)O(3) ceramics

Ceramics based on the systems of Y2O3-ZrO2 are widely used as constructional materials, catalist carriers, high-temperature oxygen sensors, materials of fuel cell and so on. In this connection, such properties of these materials as mechanical strength and cracking resistance are of exceptional importance. Phase transitions, producing changes in the chemical composition, crystal structure, and thermodynamic properties of ceramic materials, may be a cause of their destruction. The subject of the present investigation is powder zirconium hydroxide, both pure and Y-stabilized. Phase transformations have been studied well enough in these powders with micron size of particles. However up to now, there have been no systematic attempts to determine an interconnection between powder dispersity and phase transitions (and associated mechanical characteristics). In present work powder precursors of various dispersity were synthesized by sol-gel method allowing to obtain particles with sizes ranging from 40 nm to 5-10 pm. The main purpose of the work was to obtain powders with narrow particle size distribution, that is, essentially monodispersed powders. To characterize the powders obtained, we used the following methods: electron microscopy, laser scattering particle size distribution analysis, and adsorption methods. Experimental results have shown that dispersity of powders under investigation has a profound effect not only on their phase transition temperatures, but also on composition of precursor crystallohydrates. Three points bending measured at 1000 degrees C for the ceramics fabricated from these precursors also depends on the precursor dispersity