Structural distortion of polycrystalline piezoelectric PbTiO3 film for high temperature application

초록

Lead titanate (PbTiO3, PT) is an important member of the group of perovskite-structured materials that exhibits useful dielectric, piezoelectric and electromechanical properties. PT has a tetragonal phase at room temperature, a high Curie temperature of 490 °C and large tetragonality (c/a = 1.06). PT undergoes large volume change during the phase transition from cubic to tetragonal structure so that pure PT ceramic or thick film could not be fabricated. Even though, it is known that nano size PT has more cubic like structure, which has smaller c/a ratio but it is not easy to fabricate the polycrystalline PT thick film with nano-grain. In this experiment, polycrystalline PT thick films with nano-grain were deposited by using an aerosol deposition (AD) method on Si wafer. Crystal structure was analyzed with XRD and piezo and ferroelectric properties were characterized. For the high temperature application around 500 oC, dielectric constant vs temperature and P-E vs temperature were measured. AD deposited PT film showed the stable ferroelectric properties up to around 250 oC without severe degradation or leakage.