Multifunctional ceramic sensors: Humidity-gas sensor and temperature-humidity sensor

Two types of multifunctional ceramic sensors have been developed in response to strong demands for automatic control systems in cooking ovens, air conditioners, etc. The first sensing device can detect both humidity and particular reducing agents, such as alcohols and smokes, with a high sensitivity and selectivity. This novel ceramic sensor utilizes gas chemisorption at 400°-500°C as well as water physisorption at <150°C on the grain surface of MgCr
2
O
4
-TiO
2
ceramic with a porous structure and p-type semiconduction. The other sensor is composed of a porous dielectric Ba
0.5M
Sr
0.5
TiO
3
ceramic characterized by a high temperature dependence of the dielectric constant. The sensing device can independently detect simultaneously and rapidly both temperature and humidity. These sensors exhibit long-term stability, in combination with heat treatment.