Pressure Sensing Using Electrostatic Capacitance
Piezoelectric ceramic pressure sensors have been attracted great interest due to their simple and miniature structure compared with conventional sensors such as strain gauge sensor. A new type of static pressure sensor by using a change of permittivity upon applied mechanical pressure has been studied in this work. BaTiO3 ceramics with/without a small amount of Mn were used as sensing materials and the effect of poling treatment on their sensor performance was investigated. An anti-ferroelectric material, NaNbO3, was also examined. All materials could detect the change of pressure through the frequency shift of CR oscillator. Change of permittivity of non-doped BaTiO3 and Mn doped BaTiO3 without poling treatment were larger than that of PZT used as a reference, that is, BaTiO3 ceramics had higher-pressure sensitivity. BaTiO3 and relative materials, however, needed transit time to reach the steady state, while NaNbO3 was independent to the time. Conclusively, it seems that BaTiO3 and relative materials without poling treatment and the anti-ferroelectric material, NaNbO3, become possible candidates as a pressure sensor using permittivity change.
T. Ohji, T. Sekino and K. Niihara
N. Bamba, N. Endo, T. Takagi, T. Fukami, "Pressure Sensing Using Electrostatic Capacitance", Key Engineering Materials, Vols. 317-318, pp. 865-868, 2006