Investigation On Synthesis Methods And Dielectric Properties Of High-frequency Ag(Nb_1-xTa_x)O₃ Based Ceramics

Based on the research trends, the Ag(Nb 1-x Ta x )O3 ceramics were prepared by the solid-state method and liquid phase method (sol-gel method) in this work. The dielectric properties of the ceramics doped with dopants were investigated. In addition, the micromechanisms influencing the dielectric properties of the ceramics were analyzed according to the dielectrics theory, sintering theory and lattice vibration theory.For the solid-state preparation of Ag(Nb 1-x Ta x )O3 ceramics, the main researches were shown as follows:(1) The main phase of Ag(Nb 1-x Ta x )O3(x=0.1~0.5)without any second phases was obtained by the solid-state method, and the heat-processing was determined. The microstructures and dielectric properties of the ceramics were investigated, and the reasons for leading to the different dielectric properties of the ceramics were discussed. These provided the foundation for improving the dielectric properties of the ceramics.(2) The high-performance products of Ag(Nb 0.8 Ta 0.2 )O 3 -CaF2 systems, with ultra high permittivity (ε>1000) and low dielectric loss, were prepared. Meanwhile, Raman testing technology was induced. The relationship between lattice vibration characteristic for the lattice modes and the dielectric properties was established, which completed the modification theory.(3) The dielectric properties of the ceramics doped with single oxide or composite oxides and rare earth elements were investigated. The mechanisms of the different dopants improving the dielectric properties were investigated. The high-performance products of ANT82-4.5wt%Bi 2 O 3 ceramics were obtained.For the sol-gel preparation of Ag(Nb 1-x Ta x )O3 ceramics, the main research works were shown as follows:(1) At the present, for the sol-gel processing techonology, niobium pentaoxide and tantalum pentaoxide were also dissoloved by using the corrosive HF and HNO3, and then the Ag-Nb-Ta precursor sol was prepared. This processing method did harm to the environment and the body health. In this work, a new processing route was proposed. The sol was prepared by using the safety alkali salt, which could dissoloved niobium pentaoxide and tantalum pentaoxide into tantalate and niobate. (2) There were rarely reports for the Ag(Nb1-xTax)O3 nanopowders by using sol-gel method. In this work, the influence of processing parameters on the stability of the sol was invesitigated systematacially. And the high-performance Ag(Nb1-xTax)O3 ceramics were obtained. The uniform mixing for the materials in molecular even atomic level was realized by using the sol-gel method, which lay foundation for the design of material compostion, structure and properties.(3) The Ag(Nb0.6Ta0.4)O3 ceramics prepared by the solid state method and sol-gel method. In this work, the different dielectric temperature characteristics for the Ag(Nb0.6Ta0.4)O3 ceramics was found for the first time. The mechanism leading to the characteristics was discussed. The realationship between lattice distortion and interfacial tension was established, which lay theoretical and experimental foundations for design and synthesis of materials structure and properties.