Formation of ceramic bodies using submicron MSnO3 (M = Ba, Zn, Ca) particles and evaluation of their electric behaviour in different atmospheres

In this work, the most suitable conditions were determined for shaping ceramic bodies of the MSnO3 system (M = Ba, Zn, Ca), using submicron particles of these perovskites synthesized by a chemical route. For this, the rheological behaviours of colloidal suspensions of the MSnO3 powders (M = Ba, Zn, Ca) were studied considering the effects of solid content and concentration of ammonium polyacrylate (APA). The results indicated that the optimal solids contents for stable suspensions in each system were 13.8 (BaSnO3), 19.4 (ZnSnO3), and 21.5 vol.% (CaSnO3). The suspensions containing BaSnO3 and ZnSnO3 showed large reductions in viscosity, approximately 87%, when APA (0.5-0.8wt.%) was added. In contrast, the CaSnO3 suspension did not show significant changes after addition of APA. Slip casting of the stable suspensions allowed formation of porous green bodies, which were subsequently sintered in the range 1000-1500 degrees C. Considering their potential use as gas sensors, a preliminary study of the sintered bodies showed high detection responses (Ra/Rg) toward 80 ppm reducing gas at operating temperature of 270 degrees C, especially ZnSnO3 to acetone and ethanol vapours, BaSnO3 to ethanol vapour and CaSnO3 to toluene vapour.