High-Temperature Methane Sensors Based on ZnGa<sub>2</sub>O<sub>4</sub>:Er Ceramics for Combustion Monitoring
The use of CH<sub>4</sub> as an energy source is increasing every day. To increase the efficiency of CH<sub>4</sub> combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH<sub>4</sub> concentration in the exhaust g...
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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Technologies |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2227-7080/13/7/286 |
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| Summary: | The use of CH<sub>4</sub> as an energy source is increasing every day. To increase the efficiency of CH<sub>4</sub> combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH<sub>4</sub> concentration in the exhaust gases of combustion systems. To this end, sensors are required that can withstand extreme operating conditions, including temperatures of at least 600 °C, as well as high pressure and gas flow rate. ZnGa<sub>2</sub>O<sub>4</sub>, being an ultra-wide bandgap semiconductor with high chemical and thermal stability, is a promising material for such sensors. The synthesis and investigation of the structural and CH<sub>4</sub> sensing properties of ceramic pellets made from pure and Er-doped ZnGa<sub>2</sub>O<sub>4</sub> were conducted. Doping with Er leads to the formation of a secondary Er<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub> phase and an increase in the active surface area. This structural change significantly enhanced the CH<sub>4</sub> response, demonstrating an 11.1-fold improvement at a concentration of 10<sup>4</sup> ppm. At the optimal response temperature of 650 °C, the Er-doped ZnGa<sub>2</sub>O<sub>4</sub> exhibited responses of 2.91 a.u. and 20.74 a.u. to 100 ppm and 10<sup>4</sup> ppm of CH<sub>4</sub>, respectively. The Er-doped material is notable for its broad dynamic range for CH<sub>4</sub> concentrations (from 100 to 20,000 ppm), low sensitivity to humidity variations within the 30–70% relative humidity range, and robust stability under cyclic gas exposure. In addition to CH<sub>4</sub>, the sensitivity of Er-doped ZnGa<sub>2</sub>O<sub>4</sub> to other gases at a temperature of 650 °C was investigated. The samples showed strong responses to C<sub>2</sub>H<sub>4</sub>, C<sub>3</sub>H<sub>8</sub>, C<sub>4</sub>H<sub>10</sub>, NO<sub>2,</sub> and H<sub>2</sub>, which, at gas concentrations of 100 ppm, were higher than the response to CH<sub>4</sub> by a factor of 2.41, 2.75, 3.09, 1.16, and 1.64, respectively. The study proposes a plausible mechanism explaining the sensing effect of Er-doped ZnGa<sub>2</sub>O<sub>4</sub> and discusses its potential for developing high-temperature CH<sub>4</sub> sensors for applications such as combustion monitoring systems and determining the ideal fuel/air mixture. |
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| ISSN: | 2227-7080 |