材料期刊网

以La(OAc)₃、Ba(OAc)₂、Ti(OⁿBu)₄为起始物, 采用共溶-水凝胶法经陈化获得湿凝胶, 干燥后制得干凝胶, 研磨过筛和埋渗电极、加压成
型为素坯, 经不同温度和保温时间烧结, 制得掺镧La_xBa_1-xTiO₃陶?瓷传感元件系列 (x=0.00, 0.05, 0.10, 0.20, 0.30), 测试其阻-湿特
性, 从中获得了具有良好特性参数的湿敏陶瓷及其主要工艺条件(x=0.10, 1350℃/1h), 阻-湿特性在工作湿度范围内(相对湿度RH=32.8%～93.6%)的平均灵敏度S=5×10⁴kΩ/RH(%), 线性相关因子r=0.998, 响应时间τ=110s, 湿滞低于4%, 湿敏选择性良好
: 对H₂, CH₄, CH₂=CH₂, CH₃CH=CH₂, CO, C₆H₆ 和CH₃CH₂OH(g)七种气体具有抗干扰性能. 应用SEM, AFM及XRF对陶瓷的显微结构和
元素含量进行测定, 确定了陶瓷的显微组织, 晶粒尺寸, 晶相结构, 表面粗糙度和全元素分析. 讨论了掺镧改性的可能机理: La³⁺不等价取代Ba²⁺, 引起Ti⁴⁺捕获一个自由电子而变价为Ti³⁺, 该?电子在适宜的陶瓷显微结构下受水分子影响易于进入导带, 使掺镧钛酸钡得以
半导化; 半径较小的La³⁺取代半径较大的Ba²⁺, 则降低四方晶相的晶格畸变度δ, 即晶轴比c/a变小, 使四方晶格的不对称性及各向
异性?降低, 从而减少陶瓷烧结后冷却过程中内应力引起的破裂.

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: r=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⁺.