Finite size effect on the sinterability and dielectric properties of ZnNb2O6-ZBS glass composites

Abstract

ZnNb2O6 (ZN) is a columbite-structured niobate compound showing excellent dielectric properties and comparatively low sintering temperatures (similar to 1200 degrees C). Hence it is a good candidate for possible low-temperature cofired ceramics (LTCC) applications. In the present investigation, ZnNb2O6 was synthesized in the form of micrometer-sized powder using a conventional solid-state ceramic synthesis route as well as in the form of nanosized powder by a polymer complex method. The finite size effect of ZN particles on sinterability and microwave dielectric properties of sintered pellets was evaluated. The phase formation was confirmed from the X-ray diffraction (XRD) analysis. The particle size distribution of the nanoparticles was found to be of the order of 18-20 nm by using high-resolution transmission electron microscopy analysis and 30 nm by analyzing the XRD patterns using Debye Scherrer's formula, after correcting for the instrument broadening effects. A ZN-60ZnO-30B(2)O(3)-10SiO(2) (ZBS) composite was made by adding predetermined amounts of glasses. The microstructures of the sintered pellets of ZN and ZN-ZBS composites were examined using scanning electron microscopy and analyzed using image analysis. The nano-ZN-ZBS composites were sintered to 93% of the reported density at 925 degrees C/2 h, with microwave dielectric properties of epsilon(r)=22.5, Q x f similar to 12 800 GHz, and tau(f)=-69.6 ppm/degrees C, emerging as a potential material for possible LTCC applications