TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process: The milling process is carried out for 15-45 minutes, preferably 30 minutes using YTZ grinding balls of 0.3-0.6 mm diameter at a speed of 1000-1500 rpm with 40-60 volume percent of solid material. A crack attenuator comprising alumina is added to the milled mixture.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: A dispersant preferably, citric acid is added to the aqueous solvent and the ratio of ceramic material to dispersant is 1/20-1/15. A binder system containing hydroxyl polymer and plasticizer is added to the milled mixture to form a slurry. The hydroxyl polymer is 25-35 weight percent of polyvinyl alcohol and the plasticizer is glycerol whose ratio to polyvinyl alcohol is 0.5-1. A defoamer and surfactant are added to the binder along with the hydroxide to adjust its pH. Preferred Matrix: The milled mixture of ceramic material is added to an aqueous solvent containing binder system to form a slurry which is then cast to form a matrix. The mean pore size of the matrix is 0.06-0.4 mum, preferably 0.2 mum diameter. The pore size distribution and the thickness of the matrix are 0.02-0.8 mum and 0.004-0.050 inches, preferably 0.006-0.015 inches, respectively. The amount of binder and crack attenuator are 10-15 wt. % and 15-20 wt. % of solid content of slurry. EXAMPLE - An aqueous solution of citric acid was added to ceramic powder containing alpha-LiAlO2 having surface area of 11.3 m2/g. The amount of ceramic powder was controlled so that the ratio of citric acid/ceramic powder became 1/20-1/10. Deflocculation was carried out in an attritor equipped with YTZ agitation shaft and YTZ grinding balls of 0.6 mm diameter. The powder was added to aqueous solution and milled for 0.5 hours at 1000 rpm. After deflocculation the aqueous mixture was separated and pored into binder system containing polyvinyl alcohol and glycerol plasticizer, to form a slurry. 0.5-1.5 g of defoamer (per 100 g of binder system) and surfactant was added to the binder system. The pH of binder system was adjusted to 11.5 using ammonium hydroxide. 15-20 wt. % of reinforcement material (alumina) particles or platelets of size 20-100 mum was added as crack attenuators. The slurry was cast to form a flexible tape with sufficient mechanical strength and microstructure. Thermogravimetric analysis for binder removal from tapes was performed and tapes became brittle but retained structural integrity after binder removal. Single cell testing of fabricated matrix showed good gas sealing efficiency. Mercury porosimetry analysis of matrix after binder removal showed mean pore size of 0.2 mum diameter with uniform pore size distribution of 0.02-0.8 mum diameter.