掺镧改性钛酸钡湿敏陶瓷传感元件的纳米组装与表征(英文)

Nano-fabrication and characterization of La-doped BaTiO_3 humidity sensing ceramic element

室温条件下，掺镧钛酸钡多晶陶瓷传感元件电阻随着湿度的增加而下降三个数量级（相对湿度变化范围：３３—９４％）。采用溶胶－凝胶工艺，以醋酸镧、醋酸钡及钛酸丁酯为起始物，湿凝胶经５０℃干燥制得干凝胶，部分干凝胶在８００℃／２ｈ的焙烧条件下制备纳米多晶粉体，另一部分干凝胶经研细过筛之后，埋渗电极和等静压成型为素坯，在１３５０—１４００℃／１ｈ的条件下烧结而成为陶瓷，再经封装和老化即组装成为陶瓷元件．元件的湿敏特性则采用ＲＬＣ－直流电桥阻抗仪加以测试，其阻－湿线性相关系数ｒ＝０．９９３１，灵敏度Ｓ＝Ｒ＿（３３％ＲＨ）／Ｒ＿（９４％ＲＨ）≥１０～３。文中利用多种手段对干凝胶原粉、掺镧多晶粉体以及陶瓷进行了结构表征．ＦＴ—ＩＲ Ｒ Ｒ干凝胶含羟基，说明凝胶前驱体发生了水解反应。ＸＲＤ证明掺镧多晶粉体及陶瓷具有四方晶相结构，原始晶粒尺寸为纳米级且随焙烧温度增高而变大（１３．６－３７．３ ｎｍ）。ＳＥＭ对粉体及陶瓷的外观形貌进行了观察：表明粉体原始晶粒发生了团聚作用，形成了不同形貌的团聚颗粒，团粒疏松而多孔．团粒的尺寸属于微米级（１—１０μｍ）；多晶陶瓷的晶粒外观呈四方晶相，尺寸分布比较均匀，平均约０．８μｍ。

La-doped BaTiO_3 polycrystalline ceramic shows a rapid decrease in electronic resistance by three of orders of magnitude at room temperature when brought into different humidity atmosphere (relative humidity range : 33-94%). In the current investigation, nanosize polycrystals were prepared by sol-gel route, in the presence of Ba(OAc)2, La(OAc)3, Ti(OnBu)4 as precursor of Ba2+, La3+ and Ti4+. The dry gel obtained by drying wet gel at 50 ℃ was calcined at different temperatures to synthesize nanosize polycrystals. Gel-to-ceramic conversion was achieved by sintering at 1350-1400 ℃/ 1h. In advance, electrode was inserted and the humidity sensor was fabricated through the cold-pressed, aged and capsulated routes. Humidity--resistance of ceramic sensor was measured via RLC DC impedimeter. The nanosize polycrystals were characterized by various techniques, such as DTA-TG, FT -IR, XRD, SEM.