Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

Abstract

Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors.

Preparation, Characterization, and Evaluation of Humidity-Dependent Electrical Properties of Undoped and Niobium Oxide-Doped TiO2 : WO3 Mixed Powders

“…Equivalent circuits have been considered as an interesting source of parameters [25][26][27] that have been associated with di erent mechanisms in overall electrical response. e circuit represented in Figure 7 has been explored by the authors in recent works [8,9], and the components are described below: C geo is used to represent the geometrical capacitance, while the bulky granular response is assigned to R 1 //C 1 .…”

Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

“…Therefore, the present novel fabrication technique and the newly developed sintered electro-ceramic nanocomposite would be very promising for advanced humidity sensor applications. Moreover, since this sensor showed excellent sensitivity and could be able to make thinner less than 1 mm [8], this material has potential for use in advanced humidity sensors for biomedical applications [41], particularly at skin–socket interfaces of an artificial stump.…”

“…The CaMgFe 1.33 Ti 3 O 12 nanocomposite was developed by solid-state step-sintering at suitable temperatures in a box furnace (XY1600, Nanyang Xinyu Furnaces, He’nan, China) using commercial ceramic powders of CaO, MgCO 3 , Fe 2 O 3 and TiO 2 (99.9% pure, Fisher scientific Ltd., Selangor, Malaysia) with proper molar ratio, as reported before [41]. The empirical formula of the unsintered nanocomposite was calculated to CaMgFe 1.33 Ti 3 O 12 from the used molar ratio of the raw ingredients.…”

“…Therefore, for the first time, we aim to synthesize Ca, Mg, and Ti oxide based complex ferrite material (probable empirical formula CaMgFe 1.33 Ti 3 O 12 ) using inexpensive solid-state step-sintering from inexpensive iron oxide (Fe 2 O 3 ), magnesium carbonate (MgCO 3 ), calcium oxide (CaO) and titania (TiO 2 ) powders and by optimizing the sintering conditions for humidity sensing application in the field of biomedical engineering. Since our previous report on capacitive sensor have shown successful effort [41], it has motivated us to carry out humidity dependent electrical impedance, complex impedance, modulus, sensitivity, linearity, hysteresis, and response and recovery time analysis measurements on nanostructured CaMgFe 1.33 Ti 3 O 12 complex ceramic samples in the present study.…”

Design and Implementation of an Infrared Radiant Source for Humidity Testing

“…Some sensors with new materials possessing resistive and capacitive features have been explored, which include a sulfonated polycarbonate resistive humidity sensor [1], polyimide-based capacitive humidity sensor [2], a high-performance capacitive humidity sensor with novel electrode and polyimide layer capacitive humidity sensors [3], and some sensors with improved sensing properties whose response and recovery times are 14.5 s and 34.27 s, respectively, for humidity levels between 33% RH and 95% RH at 102 Hz. [4]. These kinds of humidity sensors often have long response times.…”