Fracture Toughness Anisotropy of Sodium β‐ Alumina

Abstract

The fracture toughness anisotropy was determined for sodium p‐alumina single crystals, using a hardness indent method. For cracks with a habit plane normal to the 00.1 planes, the fracture toughness is ∼2 MPa.m112, whereas for cracks running parallel to the 00.1 planes, it is ∼0.16 MPa.m112. This extreme anisotropy may partly explain the difference between calculated and observed critical current densities jor mode I failure initiation of poly crystalline solid electrolytes.

Interfacial reaction behavior and thermal stability of barium zirconate-coated alumina fiber/alumina matrix composites

“…26 Many alkali, alkaline-earth, and rare-earth cations can stabilize the hexaluminate structure in either ␤-Al 2 O 3 or MP form. 27 29 Besides, Cain et al 34 proposed an in situ reaction approach through reactions between a simple fiber coating and surrounding matrix to obtain a hexaluminate interphase.…”

Fabrication and Testing of Oxide/Oxide Microcomposites with Monazite and Hibonite as Interlayers

“…In the case of monazite, microstructures of fractured microcomposites (Figs. [5][6][7][8] show clear evidence for debonding at the coating/matrix interface, confirming that the interface between monazite and matrix Al 2 O 3 is sufficiently weak to debond under axial loading of the composite in tension. Fractographs of hibonite-containing composites show evidence for crack deflection, but the debond crack is not sustained beyond a few micrometers.…”

“…The hexaluminate shows a high preference for basal cleavage with a fracture anisotropy of >5. 5 Extensive work on the processing of fiber coatings of calcium hexaluminates has been reported recently. 1,[6][7][8][9][10] While significant progress has been made in obtaining uniform coatings of monazite and hibonite on monofilaments, there is only indirect evidence suggesting that these coatings actually prove effective in producing tough ceramic composites.…”

Influence of the Kinds of Aluminum Source on the Preferential Orientation and Properties of Na.BETA.-Alumina Ceramics

“…6 In this case, it would be interesting to determine the preferential changes in the crystalorientation-dependent mechanical strength and ionic conductivity.…”