Fabrication and characterization of compositionally graded PbxSr1−xTiO3 thin films by the Sol–gel method

Different compositionally graded PbxSr1−xTiO3 (x = 0.2, 0.3, 0.4, 0.5 and 0.6; PST) thin films were deposited on LaNiO3(LNO)-buffered stainless steel (SS) substrates. Both LNO and PST thin films were prepared by the sol–gel method. X-ray diffraction and scanning electron microscopy analysis were used to investigate the crystallinity and surface morphology of PST thin films. It showed that the crack-free PST thin films presented pure perovskite phase. The dielectric permittivity was measured in the frequency range of 103–106Hz. The tunable value of compositionally graded PST films can be as high as about 30 % (measured at E = 300 kV/cm, 105Hz). The LNO-buffered layers can effectively reduce the dissipation constant of PST films on SS, which was about 3 % and in the same level with the PST films deposited on traditional Si substrates. The temperature and frequency stability of tunability has been improved. The value of (Δnr/nrTo) % (rate of tunability change) could be less than 5 % in the most range of temperature, which demonstrated that PST could be a promising candidate material for tunable devices applications.