| The microwave tunable ferroelectric materials have been widely applied in many fields especially in microwave tunable devices, such as phase shifter in phased array antenna, resonantor and filter etc. As far as microwave tunable dielectric materials, Barium strontium titanate(BST) and its doped series have been investigated intensively. Recently, Cross etc. found that lead strontium titanate (PST) has bigger tunability and lower loss, besides this, PST is a perovskite ferroelectric material which has good solid solution. Because of the expedient modulation of curie temperature Tc to room temperature, the larger dielectric-temperature coefficients, PST materials are favorable to be used in microwave tunable devices. Compared with BST materials, especially in thin films, PST has smaller ferroelectric critical size, lower crystallization temperature, and compatible fabrication with Si micro-electronics, so it can meet the need of the high quality si-based integrate circuit (IC). MoreOver, it is important to promote the development of the miniaturization and integration for the modern devices. At present there are a few research on the PST materials, especially on the thin films, and the properties of the thin film is far away to the expectation. In this thesis, the sol-gel preparation and characteristics of the PST thin films were investigated in detail, and got the high quality PST thin films.This thesis reviewed the development of the microwave tunable ferroelectric thin film materials, summarized the application of sol-gel on the materials, and introduced the principle and application of the microwave tunability in brief.The Mg doped Pb0.4Sr0.6MgxTi1-xO3-x (PST) thin films in the perovskite structure primarily were fabricated successfully on ITO/glass substrates by the sol-gel method with different heat processing. It is found that both the formation of the perovskite and contents of the crystalline phase in this PST thin film were dependent on the preparation processing and Mg doping content. The crystalline phase structure of the film with proper Mg doping content (x=0.01-0.03) can be modified which made the crystallization easier, and then the crystalline content in the film was improved. Onthe other hand, heat processing also effected the crystallization. When Mg doping content exceed certain content, the longer of the heat processing time, the lower the crystalline content.The permittivity of the film and the insulation property in low frequency was affected by Mg doping. At x=0.01 -0.03, the intrinsic oxygen vacancy were balanced by the Mg doping. The crystalline phase structures of the films were complete which improved the crystalline content at some extent. Then the permittivity of the films reached a maximum, and at the same time, the relaxation of the dielectric loss happened at a lower frequency.It can be found that the heat temperature would influence the permittivity of the film with two opposite action. The permittivity of the film has a maximum with the increasing of the heat processing temperature. At lower temperature, the increase of the crystalline content with the increase temperature dominated in the effect on the improvement of the permittivity. With the temperature increasing further, more excessive oxygen vacancies that might deteriorate the permittivity were created. The permittivity decreased at certain temperature.The dielectric tunability of the films changed with the different measure frequency. At lOOKHz, the tunability of the films was bigger than at other frequency, about 20-30% (under bia 24V). The dissipation factor of the films was about 0.5 at zero bias. Considering the two factors, the K factor was calculated at 10~1 magnitudes.
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