Vapor-phase synthesis of mesoporous SiO2-P2O5 thin films.
Mesoporous SiO2-P2O5 films were synthesized from the vapor phase onto a silicon substrate. First, a precursor solution of cetyltrimethylammonium bromide (C16TAB), H3PO4, ethanol, and water was deposited on a silicon substrate by a spin-coating method. Then, the C16TAB-H3PO4 composite film was treated with tetraethoxysilane (TEOS) vapor at 90-180 degrees C for 2.5 h. The H3PO4-C16TAB composite formed a hexagonal structure on the silicon substrate before vapor treatment. The TEOS molecules penetrated into the film without a phase transition. The periodic mesostructure of the SiO2-P2O5 films was retained after calcination. The calcined films showed a high proton conductivity of about 0.55 S/cm at room temperature. The molar ratio of P/Si in the SiO2-P2O5 film was as high as 0.43, a level that was not attained by a premixing sol-gel method. The high phosphate group content and the ordered periodic mesostructure contributed to the high proton conductivity.
Nishiyama
Norikazu
N
Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan. nisiyama@cheng.es.osaka-u.ac.jp
Kaihara
Junji
J
Nishiyama
Yuko
Y
Egashira
Yasuyuki
Y
Ueyama
Korekazu
K
D008567:Membranes, Artificial; D010316:Particle Size; D017553:Phosphorus Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D016062:Porosity; D012825:Silicon / Q000737:chemistry; D012822:Silicon Dioxide / Q000138:chemical synthesis* / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature
D008567:Membranes, Artificial; D017553:Phosphorus Compounds; C012500:phosphorus pentoxide; D012822:Silicon Dioxide; D012825:Silicon