Vapor phase synthesis of ordered mesoporous silica-phosphate complex films and their proton conductivity

Abstract

Abstract Ordered mesoporous silica-phosphate complex films were prepared by a vapor phase method. First, a block polymer (Brij 30: C 12 EO 4 ) /H 3 PO 4 composite was deposited on a silicon substrate. The Brij 30/H 3 PO 4 composite film was treated with a tetraethoxysilane (TEOS) vapor. The TEOS vapor was infiltrated into the film, resulted in a phase transformation of the silica-phosphate/Brij 30 composite. The periodic structure of the mesostructured silica-phosphate complex film was retained after calcinations. The silica-phosphate complex films prepared by the vapor-phase method showed a high proton conductivity of about 0.1 S cm –1 . The measured P/Si molar ratio in the film was 0.14. Such a high content of P cannot be attained by a sol-gel method because of a collapse of an ordered structure. Both the high content of phosphate groups in and on the pore wall and the highly ordered periodic structure must contribute to the high proton conductivity of the silica-phosphate complex films.