多孔硅湿敏元件的频率特性

用多孔硅作为湿敏元件, 室温下在20Hz~100kHz频率范围,湿度从11%RH升至95%RH进行实验。结果表明:不同测试频率对多孔硅湿敏元件有较大影响,低频范围测量灵敏度高;高频范围效果不佳。讨论了频率影响的机理,其理论分析和实验结果一致。     

铁酸镧与高分子复合材料湿敏元件特性分析

采用纳米铁酸镧与高分子复合材料制成湿敏元件。研究了复合材料和湿敏元件的制作,测试讨论了灵敏度、湿滞、电容特性、阻抗特性、响应 恢复时间等湿度敏感特性。结果表明:元件的灵敏度较高、湿滞较小,元件的电容值和阻抗值随频率与相对湿度而变化。     

退火对电容型硅纳米孔柱阵列湿度传感器性能的影响

基于硅纳米孔柱阵列(Si-NPA)制备电容型湿度传感元件,并在250℃、450℃和550℃三个温度下对元件进行退火处理。测试数据显示,在测试温度低于550℃时,Si-NPA湿敏元件灵敏度随退火温度的升高而增大,但响应时间略微延长,湿滞回差略微增大;550℃退火后,元件的灵敏度急剧降低。采用场发射扫描电镜(FE-SEM)对不同温度退火的硅纳米孔柱阵列表面形貌进行观察,发现550℃退火元件的微观多孔结构发生了明显变化,即多孔结构致密化。结果表明,通过合适温度退火可以显著提高Si-NPA湿敏元件灵敏度,同时仍然保持较快的响应速度和较小的湿滞回差。     

钛酸钡湿敏元件的介电特性

制备了电阻式纳米钛酸钡湿敏元件,测试了元件的阻抗、电容,以及介电损耗特性.测试频率对元件的阻抗-相对湿度特性曲线影响较大,特别是低湿范围.100 Hz时曲线的线性度最好.元件的电容在低频范围随相对湿度的升高而增大,但高频范围几乎不随相对湿度变化.在10～105 Hz频率范围内,湿敏元件在11%～98%RH范围都出现了介电损耗的极大值,而且随着相对湿度增大,介电损耗极大值向高频方向移动.分析实验结果,在环境水分子浓度变化时,不仅电阻式湿敏元件感湿材料的电阻发生变化,介电常数也发生变化,水分子的极化也同时存在,但是其电阻随相对湿度的变化最为明显.     

陶瓷传感器的现状与发展趋势

4.湿度传感器多孔陶瓷湿敏元件的测湿范围宽(1～100%RH)、工作温区宽(1～400℃)、响应时间短(5～30s),因而成为主要的湿度传感器.按导电机制分有离子型、电子型和介电型[50],按温度分有常温类和高温类,还有相对湿度类和绝对湿度类之分.本文则按材料的结构类型,分述尖晶石型、钙钛矿型和其它结构多孔陶瓷.     

高分子薄膜电容式湿敏元件

本文叙述高分子薄膜电容式湿敏元件的研制意义,测湿原理、湿敏元件的构造,感温材料的感湿机理、湿敏元件的性能。性能包括感湿特性,响应特性,温度特性,频率特性,耐湿耐水性,长期稳定性等。湿滞回差小,线性好,响应时间短,温度系数小,稳定性好是所研制的湿敏元件的突出特点。电容式湿敏元件是非常有前途的一类湿敏元件。     

基于Si-NPA的BaTiO3薄膜的电容湿敏性能研究

采用溶胶-凝胶和旋涂技术制备了基于Si-NPA的BaTiO3薄膜(BaTiO3/Si-NPA).场发射扫描电镜和X射线衍射实验表明,钙钛矿结构BaTiO3薄膜很好地覆盖了Si-NPA表面.通过蒸镀双面梳状电极,制作了电容型BaTiO3/Si-NPA湿敏元件并对其湿敏性能进行了测试.结果表明,室温下湿敏元件在11%～95%RH范围内具有很高的灵敏度和较快的响应速度,且电容值的对数对湿度呈现出很好的线性.虽然该薄膜湿敏元件在不同湿度下均存在温度漂移,但分析表明这种漂移有可能通过电极设计或信号补偿加以解决.     

WO_3/Si-NPA复合薄膜的电容湿度传感性能研究

制备了基于硅纳米孔柱阵列(Si-NPA)的WO3/Si-NPA复合薄膜,并对其表面形貌进行了表征,研究了其电容湿度传感性能和基点电容的温度漂移。研究表明:WO3/Si-NPA继承了衬底Si-NPA规则的阵列结构的表面形貌特征,WO3的沉积形成了连续的WO3薄膜,WO3/Si-NPA是一种典型的纳米复合薄膜。室温下,WO3/Si-NPA的电容值随测试频率的增加而单调减小,但其灵敏度则在100 Hz时达到最大值。在此测试频率下,当环境的相对湿度从11%RH增加到95%RH时,元件的电容增量高达16 000%,显示WO3/Si-NPA对环境湿度有较高的灵敏度。同时,电容的湿度响应曲线显示出很好的线性。对其基点电容的温度稳定性研究表明:WO3/Si-NPA用作湿度传感的最佳工作温度区为15~50℃。     

以石墨粉为造孔剂制成的多 孔湿敏陶瓷及其特性分析

本文报道的钴铁尖晶石多孔湿敏陶瓷,具有电阻率低,电阻和相对湿度呈线性关系的特点。该材料制成的湿敏元件不需要加热清洗,性能稳定。以石墨粉为造孔剂制成多孔湿敏陶瓷,可以提高湿敏元件的湿度灵敏度,并且有利于改进湿敏元件的长期稳定性。最后,讨论了石墨的钝化作用。     

多孔硅相对湿度传感器的设计

基于对三明治型与平铺型两种多孔硅湿度传感器结构的灵敏度分析与比较,结合两种结构的优点,设计出新的传感器的结构。通过对该结构湿度传感器的性能测试,得出该传感器的灵敏度为1.1 pF/RH%,响应时间为73 s,温度湿度系数为0.5%RH/℃,该湿度传感器适用于在中低湿环境中测量,在每隔20 d的时间对传感器跟踪测试,证明该传感具有较好的稳定性。此外为了传感器可以自解吸附,该传感器采用多晶硅为传感器加热除湿,在金属电极上溅射一层钝化层以防止电极被水汽腐蚀。     

Humidity sensing and electrical properties of a composite material of nano-sized SiO2 and poly(2-acrylamido-2-methylpropane sulfonate)

A composite material of nano-sized SiO₂ and poly(2-acrylamido-2-methylpropane sulfonate) (poly(AMPS)) was used to make a humidity sensor. The infrared (IR) spectra and microstructure of the material were analyzed, and the humidity sensing and electrical properties of the sensor were measured. The sensor well responded to humidity with a relative good linearity, though it depended on the applied frequency. The temperature influence between 15 and 35 °C was −0.71 and −0.15% RH/°C at 30 and 90% RH, respectively. The sensor showed a negligible hysteresis and fast response time upon humidification and desiccation. The stability of the sensor in a highly humid and alcoholic environment increased with increasing the SiO₂ content. The activation energy for conduction reduced with water adsorption. The different impedance plots observed at low and high relative humidity suggested different sensing mechanisms of the SiO₂/poly(AMPS) composite material.     

用复阻抗法分析纳米钛酸钡湿敏元件感湿机理

用复阻抗方法对硅衬底纳米钛酸钡湿敏元件的感湿机理进行了分析。实验测量了湿敏元件在不同相对湿度下的复阻抗特性曲线及阻抗、电容等参数随频率的变化曲线。分析出相应的等效电路,推导了等效电路有关参数,分析讨论了纳米钛酸钡湿敏元件的感湿机理。低湿时,感湿材料本身颗粒电阻和电容及吸附的少量水分子共同起作用;高湿时,吸附的水分子电离和极化起主要作用。     

基于LCP衬底的柔性湿度传感器研究

介绍了一种新型柔性电容式湿度传感器.该柔性电容式湿度传感器采用液晶高分子聚合物(LCP)作为衬底,金属铜(Cu)作为叉指电极,聚酰亚胺(PI)作为湿度传感器的湿敏介质.LCP衬底的应用使得该传感器具有良好的柔性和可弯曲性.该柔性湿度传感器与传统硅基湿度传感器相比较具有成本低廉、结构简单、制作方便等优点.该柔性湿度传感器在25℃下的平均灵敏度为0.04%pF/%RH,最大回滞为±4.16%RH,其平均灵敏度在25℃~70℃范围内受温度影响较小.在25℃下其响应时间和恢复时间分别为36 s和39 s.该柔性湿度传感器可以应用于环境湿度检测、人工电子皮肤系统和可穿戴设备等领域.     

All-optical hydrogen sensor based on a high alloy content palladium thin film

Optical reflectance measurements were performed to determine the hydrogen response characteristics of 20 nm thick Pd_0.6Au_0.4 films. The response time and signal change characteristics were determined as a function of hydrogen concentrations ranging from 0.05% to 4% in a balance of dry CO₂ free air. The detection limit was determined to be 0.05%, with a corresponding response time of 130 s, while at 4% hydrogen concentrations the response time was 5 s at ambient temperatures. A linear decrease of both the signal change and response time was measured within an operating temperature range between 25 °C and 100 °C for a 1% hydrogen in air gas mixture. The sensor response dependence of the Pd_0.6Au_0.4 film with a change in humidity was determined between ambient levels and 95% relative humidity (RH). While the signal change was independent of humidity the response time increased due to water adsorption on the Pd alloy sensing layer. A similar increase in response time was shown for 100 ppm of background CO mixed with 1% hydrogen in nitrogen at room temperature. At an elevated operating temperature of 80 °C, 100 ppm of CO did not affect the sensor response towards 1% hydrogen in a balance of nitrogen. Reliability tests have been performed over a 1-year time period and the sensing specifications have not drifted beyond 2% and 13% of the calibrated signal change and response time, respectively. A response time on the order of seconds and the proven stability of the high alloy content Pd thin film demonstrate the promising attributes of this material for use in an all-optical hydrogen sensor.     

ZrO2:TiO2复合纳米纤维湿度传感器的直、交流特性研究

利用ZrO2:TiO2复合纳米纤维制作了特性良好的电容型湿度传感器.该湿敏元件在100 Hz测量频率下灵敏度较高,线性度较好.其电容值在11％ ～98％相对湿度范围内从20 pF变化到1.5×105 pF.文中从直流特性(伏安特性、极性反转瞬时性)和交流特性(复阻抗)的角度分析了该湿敏元件的感湿机理.利用瞬时直流极性反...     

Thin polymer film based rapid surface acoustic wave humidity sensors

Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) thin films, deposited on the surface of glass slides, were studied using transmission FTIR spectroscopy upon varying relative humidity (RH) from 2 to 70%. The obtained data revealed fast dynamics of water vapor adsorption-desorption with responses on the order of several seconds. Based on the fast FTIR signal intensity changes versus RH, it was proposed that a similar rapid response can be achieved for PVA and PVP coated SAW devices due to changes in mass-loading and film viscoelastic properties upon absorption of water vapor in the films. Sub-micron thickness films were spin-coated onto the surface of LiNbO₃ SAW substrates. Both PVA and PVP based humidity sensors revealed prompt reversible response to variations in humidity, although PVP-based device demonstrated better sensor parameters with total insertion loss variation of about 50 dB over the studied RH range and response time 1.5 s for the humidity step 5-95% (recovery time - 2.5 s), representing one of the fastest SAW-based humidity sensors reported to date.     

Characterization and humidity sensing properties of Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 powder synthesized by metal-organic decomposition

Bi_0.5Na_0.5TiO₃-Bi_0.5K_0.5TiO₃ (BNT-BKT) powder is synthesized by a metal-organic decomposition method and characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A humidity sensor, which is consisted of five pairs of Ag-Pd interdigitated electrodes and an Al₂O₃ ceramic substrate, is fabricated by spin-coating the BNT-BKT powder on the substrate. Good humidity sensing properties such as high response value, short response and recovery times, and small hysteresis are observed in the sensing measurement. The impedance changes more than four orders of magnitude within the whole humidity range from 11% to 95% relative humidity (RH) at 100 Hz. The response time and recovery time are about 20 and 60 s, respectively. The maximum hysteresis is around 4% RH. The results indicate that BNT-BKT powder is of potential applications for fabricating high performance humidity sensors.     

Highly sensitive humidity sensor at low humidity based on the quaternized polypyrrole composite film

Polypyrrole composite was fabricated by using chemical polymerization at room temperature, which was further quaternized with 1,4-bromobutane to prepare the humidity sensitive material. The electrical properties of the sensor were measured. The results showed that the quaternized polypyrrole composite film exhibited low impedance at very low humidity; the impedance value was about 780 kΩ at 11% RH and the impedance changed from 10⁶ to 10³ Ω between 11% and 95% RH, which was suitable for detection of low humidity. Moreover, the logarithm of impedance of the polypyrrole composite film varied linearly (R² = 0.9916) with relative humidity in the range of 11–95% RH. Surface and cross-sectional morphology of the films, response–recovery time and hysteresis were also measured and estimated. The sensing mechanism of the sensor was also investigated.