Preparation Property and Structure of La~(3+)-doped Barium Titanate Humidity Sensing Ceramic Element

Sol precursors were prepared by the cosolubilized hydrousgel process using titanium butoxide and lanthanum acetate as well as barium acetate. After condensation and drying, the wet gel and dry gel were obtained respectively. Dry gel ground and screened was pressed into disc and sintered at different temperatures for holding different time to fabricate ceramic sensors. The measurement of humidity sensitivity and gas/alcoholic sensitivity (seven kinds of gases H2, CH4, CH2=CH2, CH3CH=CH2, CO, C6H6 and gaseous CH3CH2OH) of these sensors were performed. The humidity sensor displays high sensitivity: S'=5×104kΩ/RH(%) (relative humidity RH=32.8%-93.6%); good linearity: τ=0.998; minimum humidity hysteresis: 4%; response time: τ=110s; and fine selectivity: sensitivity-less to above seven kinds of gases. The microstructure was characterized by SEM, AFM and XRF to confirm the morphology, perovskite phase and surface roughness and whole element analysis. The mechanism of lanthanum modification was discussed that titanium ion Ti4+ can capture a free electron. It is easy for this electron to jump into the conduct band due to non-equivalent substitution of Ba2+ by rare earth ion La3+.