TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The compact layer beta -aluminum oxide ceramic powder has a particle size of 20-150 nm. The ceramic powder of porous support layer is beta -aluminum oxide or beta ''-aluminum oxide having a particle diameter of 0.5-2 mu m.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The cast slurry material has a viscosity of 1000-2000 mPa.s. The casting compact layer and scraper has a gap of 2-125 mu m. The casting porous support layer and scraper has a gap of 125 mu m to 1.5 mm. The tank liquid level is 0.3-2.5 cm. The casting flow rate is 0.5-1 cm/second. The baseband of porous support layer casting uses a silane-coated release agent polyester film baseband having a thickness of 70-650 mu m. The compact layer casting uses sintering molded porous support layer or unsintered support layer. The multi-layer composite flat plate type solid electrolyte has 2-3 layers; compact layer thickness of 10-115 mu m; and porous support layer thickness of 115 mu m to 1.25 mm. The porous support layer has an aperture of 10-85 mu m. Preferred Method: The casting process uses a drying room temperature of 40-60 degrees C. The solid electrolyte sintering temperature is 1450-1600 degrees C. The multi-layer composite flat plate type solid electrolyte is prepared by directly casting composite, compositing casted porous support layer and compact layer blank band based on the required overlapping layer, hot pressing or cold pressing the composite.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The solvent is ethanol and water, ethanol and toluene, ethanol and normal hexane, ethanol and butanone, butanone and methanol or trichloro ethylene and methanol binary azeotrope solvent system. The dispersant is triethyl phosphate, ammonium polymethacrylate, glycerol trioleate, ethoxylated castor oil or herring oil. The adhesive is polyethylene alcohol, polyvinyl butyral, latex, poly(methyl methacrylate), methyl cellulose or carboxymethyl cellulose. The plasticizer is glycerol, polyethylene glycol, dibutyl phthalate, dioctyl phthalate or triethylene glycol. The pore-forming agent is ammonium carbonate, ammonium bicarbonate, ammonium chloride, carbon powder, sawdust or starch.