NASICON thick film-based CO2 sensor prepared by a sol-gel method

Thick films of NASICON (Na+ conductor, Na3Zr2Si2PO12) were prepared for the fabrication of a planar CO2 sensor. The powder of a precursor of NASICON, derived through a sol-gel process, was screen-printed on an alumina substrate and converted into a NASICON thick film by calcination. The formation of crystalline NASICON was almost complete after calcination at 900 and 1000 degreesC, but the films remained rather poor in densification. On the other hand, the films were densified after calcination at 1100 degreesC or above, but NASICON phase disappeared by decomposition. The planar CO2 Sensor device was thus fabricated by using the NASICON thick film (30 gm thick) calcined at 1000 degreesC. The device attached with a binary carbonate auxiliary phase (Li2CO3-BaCO3) showed fairly good CO2 sensing properties at 450-600 degreesC. despite rather poor densification of the thick film used. (C) 2001 Elsevier Science B.V. All rights reserved.