A Double Layer Sensing Electrode “BaTi(1-X)RhxO3/Al-Doped TiO2” for NO2 Detection above 600 °C

Abstract

NO 2 emission is mostly related to combustion processes, where gas temperatures exceed far beyond 500˝C. The detection of NO 2 in combustion and exhaust gases at elevated temperatures requires sensors with high NO 2 selectivity. The thermodynamic equilibrium for NO 2 /NO ě 500˝C lies on the NO side. High temperature stability of TiO 2 makes it a promising material for elevated temperature towards CO, H 2 , and NO 2 . The doping of TiO 2 with Al 3+ (Al:TiO 2 ) increases the sensitivity and selectivity of sensors to NO 2 and results in a relatively low cross-sensitivity towards CO. The results indicate that NO 2 exposure results in a resistance decrease of the sensors with the single Al:TiO 2 layers at 600˝C, with a resistance increase at 800˝C. This alteration in the sensor response in the temperature range of 600˝C and 800˝C may be due to the mentioned thermodynamic equilibrium changes between NO and NO 2 . This work investigates the NO 2 -sensing behavior of duplex layers consisting of Al:TiO 2 and BaTi (1-x) Rh x O 3 catalysts in the temperature range of 600˝C and 900˝C. Al:TiO 2 layers were deposited by reactive magnetron sputtering on interdigitated sensor platforms, while a catalytic layer, which was synthesized by wet chemistry in the form of BaTi (1-x) Rh x O 3 powders, were screen-printed as thick layers on the Al:TiO 2 -layers. The use of Rh-incorporated BaTiO 3 perovskite (BaTi (1-x) Rh x O 3 ) as a catalytic filter stabilizes the sensor response of Al-doped TiO 2 layers yielding more reliable sensor signal throughout the temperature range.

Adsorption Kinetics of NO2 Gas on Pt/Cr-TiO2/Pt-Based Sensors

“…However, this Ti:O ratio is about ≈0.80:2.10; thus, one can conclude that the gradient of O 130 concentration holds even after 800 °C heat treatment (Figure 5c,d). This is also affirmed by the Pt 266 peaks in the annealed samples, which showed extended inclination into TiO2 from the bottom electrode; such observations were also mentioned in previous reports [36]. From the GDOES analysis shown in Figure 5, it is noticeable from the variation in quantitative elemental distribution profile that both the as-coated samples consist of a highly non-stoichiometric TiO 2−x layer as the O 130 has a decreasing trend, while Ti 399 has an increasing trend; see Figure 5a,b.…”

“…However, this Ti:O ratio is about ≈0.80:2.10; thus, one can conclude that the gradient of O 130 concentration holds even after 800 • C heat treatment (Figure 5c,d). This is also affirmed by the Pt 266 peaks in the annealed samples, which showed extended inclination into TiO 2 from the bottom electrode; such observations were also mentioned in previous reports [36].…”

Review: Influences of Semiconductor Metal Oxide Properties on Gas Sensing Characteristics

“…Previous literature demonstrate that sensing materials based on SnO 2 and TiO 2 nanostructures yield high selectivity sensors through either their surface modification with NM loading or bulk doping with redox capable elements thus facilitating the selective gas detection in mixed gas environments. These studies indicate that the improvement of sensing performance in such cases is due to the creation of new active centers on the MOx surface or changing the electronic structure of material (Saruhan et al, 2013(Saruhan et al, , 2016Liu Y. et al, 2017;Majhi et al, 2018;Yin et al, 2019;Raza et al, 2020).…”

Impact of Oxalate Ligand in Co-Precipitation Route on Morphological Properties and Phase Constitution of Undoped and Rh-Doped BaTiO3 Nanoparticles

“…Relying on excellent dielectric, ferroelectric, piezoelectric and optical properties, BaTiO 3 is a well-known electro-ceramic material that is used in the manufacturing of thermistors, dielectric ceramic capacitors [4][5][6] and also applied as photocatalyst and gas sensor material [7,8]. These properties of BaTiO 3 are strongly influenced by the existing polymorphs which are linked to the preparation method as well as the dopant.…”