Structural, electrical and dielectric studies on (1-x)MgTiO_3 -x Ba_(0.5)Sr_(0.)5TiO_3 composite ceramics for type-Ⅱ capacitor applications

摘要

The structural, microstructural, electrical and broadband dielectric properties of (1-x)MgTiO3-xBa(0.5)Sr(0.5)TiO(3) (for x=0.1 to 0.5) composite ceramics has been reported. Conventional solid state reaction method is followed for preparation of the powder and maximum densification is optimized at different sintering temperatures (1250 to 1400 degrees C). The structural studies revealed presence of both MTO and BST phases independently. The cryogenic dielectric response was studied over a broadband frequency range. The composite ceramics have exhibited diffused transition as a typical signature of relaxor ferroelectrics with temperature. Modified Curie-Weiss law is implemented and calculated the diffuseness constant to probe the relaxor behavior of the ceramics. The Impedance analysis in complex plane showed non-Debye type relaxation behavior. Correlated barrier hopping mechanism is found to be responsible for conduction process at higher frequency region in AC-conductivity analysis. The thermal stability of capacitance over the temperature range of (RT) -30 to +85 degrees C determined and found to be similar to-54%. The 0.7 MTO0.3 BST ceramic composite sintered at a temperature (T-s) of 1350 degrees C is optimized as the best composition with the highest values of relative density (similar to 97%), high dielectric permittivity epsilon(r)similar to 57 and quality factor, Qxf(0)=19,30GHz at 4.16GHz. The obtained properties of the composite ceramics is promising for type -II capacitors in integrated circuits of de-couplers and filters.