Microstructure and physical properties of directionally solidified alumina-zirconia eutectic composites

Abstract

Relationships between nominal composition, preparation conditions, phase composition, microstructure, and physical properties (fast ionic conductivity, dielectric response, microhardness, cracking process) are reported. It is shown that the properties depend not only on well defined parameters (nominal and phase compositions, growth rate, annealing etc.) but also on a spurious contamination of the melt which results in growth irregularities and a porosity of the composites.

Phase composition, microstructure and electrical properties of alumina-zirconia eutectic composites

“…At certain growth conditions (lower amount of stabilizers, higher growth rate), the A1203 phase, growing along the [001] direction, tends to facet the crystallization front. Due to a hypereutectic composition of the melt, the samples tl, t2 and t3 contain also ZrO 2 dendrites, [5]. 3 b,c).…”

“…Fine zirconia fibers (Fig. 3b) starts at growth velocities higher than 40 mm/h [5]. They form well defined eutectic colonies in the alumina matrix.…”

“…Space charge effects, adsorption effects, percolation effects, and a formation of new phases are supposed to be responsible for this conductivity enhancement [3]. In eutectic systems, maximum conductivity is usually observed near the eutectic composition [5]. In eutectic systems, maximum conductivity is usually observed near the eutectic composition [5].…”

“…Directional solidification of superionic eutectic composites allows to obtain highly anisotropic multiphase structures with regularly arranged components [6]. In some eutectic composites, not only the interphase distance but also the type of the microstructure depends on the growth characteristics [5]. When the volume fraction of one of the phases is lower than 0.29, a fibrous or rod-like microstructure appears.…”

“…A rather good ionic conductivity [5], excellent mechanical properties and corrosion resistance [1,[7][8][9] characterize the alumina -zirconia eutectic composites at high temperatures. A rather good ionic conductivity [5], excellent mechanical properties and corrosion resistance [1,[7][8][9] characterize the alumina -zirconia eutectic composites at high temperatures.…”