Catalytic Combustion‐Type Hydrogen Sensor Using BaTiO₃‐based PTC Thermistor

Abstract

A catalytic combustion-type gas sensor using a positive temperature coefficient (PTC) thermistor, which shows a sharp resistance change around Curie temperature, was developed for the detection of hydrogen. La-doped BaTiO 3 (Ba 0.998 La 0.002 TiO 3 ) was prepared through a solid-state method and an oxalic acid method. La-doped BaTiO 3 obtained by the oxalic acid method showed improved PTC properties, due to the formation of fine particles, as compared to that prepared with the solid-state method. The resulting sensor device showed a fairly high H 2 sensitivity in the range of 100-1000 ppm. In addition, the H 2 sensitivity and response speed were improved by coating a Pt/SiO 2 catalyst on the sensor device because the catalytic combustion efficiency of H 2 was improved by the catalyst coating.D. Damjanovic-contributing editor Manuscript No. 32105. J ournalMoreover, we also investigated the effect of a Pt-based combustion catalyst on the sensor response.

Barium titanate-based thermistors: Past achievements, state of the art, and future perspectives

“…35. 320 Riegel and H€ ardtl also reported the use of a combination of PTCR thermistors for the selective calorimetric detection of binary combustible gas mixtures for advanced process and environmental control. 321 Therefore, these devices have applications in combustion control processes, such as in automobile exhaust/and engine management systems for more efficient burning.…”

“…This results in a change in the electrical conductivity or capacitance of the material. 320 Additionally, humidity detection is of great importance in many industrial processes as well as domestic applications, such as air conditioning systems. 324,330 These materials exhibit a change in electrical conductance or capacitance due to water chemisorption at low pH 2 O and capillary condensation within the pores at higher pH 2 O, as shown by Viviani et al 331,332 This sensing effect is attributed to chemisorbed water molecules releasing electrons into the conduction band.…”

Abnormal resistivity-temperature characteristic in fluorite type Bi/K-substituted ceria ceramics

“…Some new types of lead-free PTC materials such as BaTiO 3 -(Bi 1/ 2 Na 1/2 )TiO 3 and BaTiO 3 -(Bi 1/2 K 1/2 )TiO 3 systems have been developed in past decade [9][10][11]. The related PTC conduction mechanisms were found to follow the Heywang-Jonker model, in which the grain boundary effect plays a key role in the resistivity jump around the Curie temperatures, as shown in the BaTiO 3 -based thermistors [6][7][8].…”

“…Meanwhile, the transition metal oxides such as VO 2 and V 2 O 3 with the metal-insulator transition feature are also of interest in practical applications and theoretical research [1][2][3][4][5]. In the traditional PTC ceramic thermistors, BaTiO 3 -based compounds are the most important ones for the practical applications [6][7][8]. To get the Curie temperatures higher than 120°C, lead (Pb) is used to substitute into the BaTiO 3 to form the (Ba,Pb)TiO 3 ceramics.…”

Thermochemical hydrogen sensor based on chalcogenide nanowire arrays

“…For example, semiconductor-type sensors, which are mainly constructed using tin dioxide (SnO 2 ) [8], must be operated at high temperature to be effective, increasing power consumption. For catalytic combustion-type sensors, detection of low concentration of hydrogen is not possible because the resistivity change is small at low concentration compared with the semiconductor-type sensor [9]. Palladium (Pd)-based sensors have often been used, but are susceptible to performance degradation when operated continuously in high concentrations of hydrogen gas.…”