In the recent past a great deal of research efforts were directed toward the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer a wide spectrum of materials and their sensitivities for different gaseous species, making it a better choice over other options. In this article a critical parameter analysis of different metal oxides that are known to be sensitive to various gaseous species are thoroughly examined. This includes phase of the oxide, sensing gaseous species, operating temperature range, and physical form of the material for the development of integrated gas sensors. The oxides that are covered in this study include oxides of aluminum, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, indium, iron, manganese, molybdenum, nickel, niobium, ruthenium, tantalum, tin, titanium, tungsten, vanadium, zinc, zirconium, and the mixed or...

Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review

This review paper focuses on interdigital electrodes-a geometric structure encountered in a wide variety of sensor and transducer designs. Physical and chemical principles behind the operation of these devices vary so much across different fields of science and technology that the common features present in all devices are often overlooked. This paper attempts to bring under one umbrella capacitive, inductive, dielectric, piezoacoustic, chemical, biological, and microelectromechanical interdigital sensors and transducers. The paper also provides historical perspective, discusses fabrication techniques, modeling of sensor parameters, application examples, and directions of future research.

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Interdigital sensors and transducers

In the food and agricultural industry, sensors are being used for process control, monitoring quality, and assessing safety. There is a growing demand for carbon dioxide (CO2) sensors in the bulk food storage sector, because CO2 sensors can be used to detect incipient spoilage and to assess CO2 levels in modified-atmosphere packages and storage structures. The market potential for reliable and inexpensive CO2 sensors is huge because of a wide range of applications in the agri-food industry. This review synthesizes information about the types of CO2 sensors, analyzes their detection processes, provides a broad overview of the innovative research on the development of sensors, sensing mechanisms, and their characteristics, and outlines future possibilities for use of CO2 sensors.

Carbon Dioxide (CO2) Sensors for the Agri-food Industry—A Review

A review of smart building sensing system for better indoor environment control

A mesoporous CaO-loaded In 2 O 3 material (with Ca/In 2 O 3 ratios ranging from 2.5 to 8.5 at %) has been synthesized and used as resistive gas sensor for the detection of CO2. A nanostructured In 2 O 3 matrix has been obtained by hard template route from the SBA-15 silica template. Additive presence does not distort the lattice of In 2 O 3 , which crystallizes in the Ia3 cubic space group. It has been proved by XRD, HRTEM, Raman and XPS measurements that samples contain not only CaO but also CaCO 3 in calcite phase as a consequence of CaO carbonation. Pure In 2 O 3 based sensors are low sensitive to CO2, whereas those containing the additive show an important response in the 300-5000 ppm range of gas concentrations. As seen by DRIFTS, the electrical response arises from the interaction between CO 3 2- and CO2, yielding bicarbonates products. The reaction is water-assisted, so that hydration of the sensing material ensures sensor reliability whilst its dehydration would inhibit sensor response. The use of CaCO 3 instead of CaO does not cause significant differences in electrical and DRIFTS data, which corroborates the important role played by carbonate species in the sensing mechanism.

A Novel Mesoporous CaO-Loaded In2O3 Material for CO2 Sensing†

A low-cost CO2 sensor in thick film technology has been developed using BaTiO3 and various semiconducting oxides. The sensing principle of this new CO2 sensor is based on changes in conductance of the metal oxides in the presence of carbon dioxide. In this report, effects of preparation parameters and effects of various additives on the sensitivity of the CO2 sensor are described, and measurements of the sensor resistance as a function of CO2 concentration are presented. The sensor is applicable over a wide range of CO2 concentrations. Humidity changes have only minor effects on the sensor response.

A novel thick film conductive type CO2 sensor

Analysis on the influence of vapor capillary aspect ratio on pore formation in laser beam welding of aluminum

Die Variation des Präparationsprozesses, wie z. B. die Menge des als Sinterhilfe eingefügten LiCl, das Sinterprofil und die Sinterreihenfolge, hat einen wesentlichen Einfluß auf die Eigenschaften des Dickschicht-Feuchtesensors. Die Edelmetall-Materialien der zur Auswertung der elektrischen Änderung in der sensitiven Schicht verwendeten Elektroden üben ebenso einen deutlichen Einfluß auf die Sensor-Charakteristik aus. Die Ergebnisse der Untersuchungen von Auswirkungen der unterschiedlichen Präparationsparameter auf die Widerstand! Feuchte-Kennlinien des tesensors werden beschrieben. Mn WO^-Dickschicht-Feuch-

Andrea Haeusler

Papers

A novel thick film conductive type CO2 sensor

Analysis on the influence of vapor capillary aspect ratio on pore formation in laser beam welding of aluminum

Dickschicht-Feuchtesensor auf der Basis halbleitenden MnWO4-Metalloxids