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 10(3)-10(6)Hz. The tunable value of compositionally graded PST films can be as high as about 30 % (measured at E = 300 kV/cm, 10(5)Hz). 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 (Delta n(r)/n(rTo)) % (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.