Novel oxygen sensor using hot spot on ceramic rod

Abstract

A novel oxygen sensor using hot spot on ceramic rod of high-T c superconductor RBa2Cu3OT_ ~ (R: rare earth element) has been developed. The hot spot appears by the self-heating of the local part on the RBa2Cu3OT_ ~ ceramic rod when a voltage above threshold is applied at room temperature. This sensor operates without any separate heater by taking advantage of the high temperature of the hot spot wherein oxide ions can diffuse easily. The oxygen concentration is determined from the value of the current flowing through the rod by utilizing the change in the resistivity of the hot spot depending on oxygen partial pressure in atmosphere. Oxygen concentration of 0 ~ 100% can be detected with high sensitivity and the response time is several seconds. The response performance of this oxygen sensor is almost the same as that of limiting-current-type zirconia sensor operating at 500°C.

Novel sponge-like structure created in GdBa2Cu3O7Kdceramics by hot spot

“…The visible glowing area was named a hot spot. The temperature of the hot spot in air was about 900 8C that is almost the same as its sintering temperature [6][7][8]. The hot spot moves to the negative electrode with the velocity of a few mm/min.…”

“…The direction of movement can be reversed by switching the polarity [5]. The appearance of the hot spot is related to the PTCR characteristic [5][6][7]. The movement of the hot spot is considered to be caused by the diffusion of oxide ions in the electric field over the hot spot [5,6].…”

“…The appearance of the hot spot is related to the PTCR characteristic [5][6][7]. The movement of the hot spot is considered to be caused by the diffusion of oxide ions in the electric field over the hot spot [5,6]. The heat treatment using the moving hot spot can be used as an improvement technique for its transport critical current density [8].…”

“…The current through the rod decreases abruptly when the hot spot appears, and remains constant with increasing voltage [6][7][8][9]. This is possible because the size of a hot spot with high resistivity increases linearly with increasing voltage [5][6][7].…”

“…This is possible because the size of a hot spot with high resistivity increases linearly with increasing voltage [5][6][7]. The rod with the hot spot can be used as a constant-current generator without any active component.…”