Normally, it is very difficult to process thin ceramic films (<10¯m) except by vapor deposition methods. This is because in traditional ceramics processing, initial powder particle sizes (typical average particle sizes, APSs >200 nm) make it difficult to realize mechanically robust thin films after sintering to full density due to excessive grain growth. One solution to this problem is to start with nanopowders (APSs <100 nm). Here we present efforts to use simple, easily available nano ¤-Al 2 O 3 (transition or t-Al 2 O 3) nanopowders (NPs) to process the subject films. Thus t-Al 2 O 3 NPs when properly dispersed, doped with 0.55 wt.% MgO and ball milled with a polymeric binder provide castable systems. Wire wound roller drawing/tape casting provides access to thin green films (1030¯m) with µ75 wt.% ceramic loadings. Following binder burnout and careful sintering to temperatures of up to 1500°C/7 h/air but preferably slightly lesser conditions leads to dense¯10¯m films with average ¡-Al 2 O 3 grain sizes of 500800 nm. At higher MgO concentrations, spinel phase separates during sintering likely inhibiting grain growth. These relatively dense films are flexible and translucent. Such films, because of their flexibility, may offer utility as catalyst supports, electronic substrates or as hard facings for other materials.

is a widely studied structural ceramic with applications as grinding media, for cutting tools, high-temperature engine components, prosthetic implants, and substrates for power electronics due to its high melting point, excellent mechanical strength, hardness, and chemical stability as well as its widespread abundance. 1-17 However, applications using pure α-Al 2 O 3 are limited by its low resistance to crack propagation, that is, poor fracture toughness (4-5 MPa m 1/2) 18,19 that can lead to catastrophic failure. 1-3 To enhance Al 2 O 3 fracture toughness, a common practice involves incorporating additives, such as tetragonal zirconia (t-ZrO 2), to increase toughness while maintaining the hardness and chemical resistance of Al 2 O 3 , commonly referred to as zirconia toughened aluminas (ZTAs). 2-6,20-29 Room-temperature stabilized t-ZrO 2 will transform to monoclinic (m-ZrO 2) if subjected to mechanical stress. This transformation is accompanied by a 4% volume expansion creating a compressive stress field in the surrounding grains, which opposes crack propagation. 2-4,20-24 In this process, some fraction of the energy needed for crack propagation