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Dielectric Properties of Materials Used for Microwave-Based NOₓ Gas Dosimeters

Title data

Walter, Stefanie ; Baumgärtner, Johanna ; Hagen, Gunter ; Schönauer-Kamin, Daniela ; Kita, Jaroslaw ; Moos, Ralf:
Dielectric Properties of Materials Used for Microwave-Based NOₓ Gas Dosimeters.
In: Sensors. Vol. 24 (2024) . - 2951.
ISSN 1424-8220

Official URL: Volltext

Project information

Project title:
Project's official title
Project's id
Hochfrequenzbasierter Hochtemperatur-Stickoxidsensor für die dosimeterartige Detektion von NOx im ppb-Bereich zur kontinuierlichen Luftqualitätsüberwachung
MO 1060/42-1

Project financing: Deutsche Forschungsgemeinschaft

Abstract in another language

Nitrogen oxides (NOx), primarily generated from combustion processes, pose significant health and environmental risks. To improve the coordination of measures against excessive NOx emissions, it is necessary to effectively monitor ambient NOx concentrations, which requires the development of precise and cost-efficient detection methods. This study focuses on developing a microwave- or radio frequency (RF)-based gas dosimeter for NOx detection and addresses the optimization of the dosimeter design by examining the dielectric properties of LTCC-based (Low-Temperature Co-fired Ceramics) sensor substrates and barium-based NOx storage materials. The measurements taken utilizing the Microwave Cavity Perturbation (MCP) method revealed that these materials exhibit more pronounced changes in dielectric losses when storing NOx at elevated temperatures. Consequently, operating such a dosimeter at high temperatures (above 300 °C) is recommended to maximize the sensor signal. To evaluate their high-temperature applicability, LTCC substrates were analyzed by measuring their dielectric losses at temperatures up to 600 °C. In terms of NOx storage materials, coating barium on high-surface-area alumina resolved issues related to limited NOx adsorption in pure barium carbonate powders. Additionally, the adsorption of both NO and NO2 was enabled by the application of a platinum catalyst. The change in dielectric losses, which provides the main signal for an RF-based gas dosimeter, only depends on the stored amount of NOx and not on the specific type of nitrogen oxide. Although the change in dielectric losses increases with the temperature, the maximum storage capacity of the material decreases significantly. In addition, at temperatures above 350 °C, NOx is mostly weakly bound, so it will desorb in the absence of NOx. Therefore, in the future development of a reliable RF-based NOx dosimeter, the trade-off between the sensor signal strength and adsorption behavior must be addressed.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: dosimeter; radio frequency (RF); LTCC; NOx; gas sensor; Microwave Cavity Perturbation; dielectric properties
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Central research institutes > Bayreuth Center for Material Science and Engineering - BayMAT
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 13 May 2024 09:15
Last Modified: 13 May 2024 12:02