Strain sensing properties of barium titanate and barium strontium titanate thin films prepared by a sol-gel techniques

Abstract

We have fabricated strain gauges from dielectric materials, barium titanate (BaTiO₃) and barium strontium titanate (BaSrTiO₃), depositing on flexible borosilicate glasses substrates using a sol-gel method. The coplanar capacitors were patterned on the surface of the films using a DC sputtering technique. The measurement of the strain on a cantilever spring made from capacitor arrays were obtained by monitoring the changing of capacitance of the dielectric films. A parallelogram clamp and a piezoelectric actuator were used for supporting the device under test as well as for the application of strain. The capacitive strain gauge was connected to the oscillator circuit via wire bonding. The changing of capacitance in capacitive strain gauge was done by applying the force with eleven values. The deflection of the beam cantilever was indicated by a dial micrometer. Also, the capacitors were diced individually to 3x5 mm and the capacitance measurements were taken as a function of Sr composition of Ba[subscript x] Sr[subscript1- x] TiO₃ and frequency with an LCR meter. The dielectric constant decreased as a function of frequency in the range of 100-1100 kHz and the maximum dielectric constant of Ba[subscript x] Sr[subscript1- x] TiO₃ films was found to be 482 at x = 0.35.