Powder-less processing for nano-structured bulk ceramics: Realization of direct fabrication from solutions and/or melts

Based upon energetic considerations for every ceramic fabrication processing via solids as powders, liquids as solutions and melts, or gases including atoms and ions, it is concluded that solution processing has the least energy consumption when the shaped ceramics can be fabricated directly. The direct fabrication of ceramics in a solution by a single step process can be achieved via the interfacial reaction between a solid, substrate and reactant, and a solute specie in a solution. These soft processing and/or soft solution processing might prepare various ceramics films like BaTiO₃, SrTiO₃, CaWo₄, LiCoO₂, etc., at low temperatures, RT-150°C, without any post firing. The patterned ceramic films can also be fabricated directly in solutions when those interfacial reactions are locally activated and/or scanned. Another direct fabrication method, the ink-jet reaction method has been developed for the direct patterning of ceramics. The novel melt processings have been re-investigated for the direct fabrication of bulk ceramics particularly for the binary and ternary eutectic systems. Melt casting and annealing of the eutectic amorphous phase could produce nano-structured ceramics in HfO₂-Al₂O ₃-GdAlO₃ and C₁₂A₇-CaYAlO ₄ systems, etc. The importance of the powder-less processings, direct fabrications, of ceramics from solutions and/or melts has been demonstrated for the future sustainable society.