Effect on the Grain Size of Single-mode Microwave Sintered NiCuZn Ferrite and Zinc Titanate Dielectric Resonator Ceramics

Abstract

Microwave sintering of materials significantly depends on dielectric, magnetic and conductive Losses. Samples with high dielectric and magnetic loss such as ferrites could be sintered easily. But low dielectric loss material such as dielectric resonators (paraelectrics) finds difficulty in generation of heat during microwave interaction. Microwave sintering of materials of these two classes helps in understanding the variation in dielectric and magnetic characteristics with respect to the change in grain size. High-energy ball milled Ni0.6Cu0.2Zn0.2Fe1.98O4-delta and ZnTiO3 are sintered in conventional and microwave methods and characterized for respective dielectric and magnetic characteristics. The grain size variation with higher copper content is also observed with conventional and microwave sintering. The grain size in microwave sintered Ni0.6Cu0.2Zn0.2Fe1.98O4-delta is found to be much small and uniform in comparison with conventional sintered sample. However, the grain size of microwave sintered sample is almost equal to that of conventional sintered sample of Ni0.3Cu0.5Zn0.2Fe1.98O4-delta. In contrast to these high dielectric and magnetic loss ferrites, the paraelectric materials are observed to sinter in presence of microwaves. Although microwave sintered zinc titanate sample showed finer and uniform grains with respect to conventional samples, the dielectric characteristics of microwave sintered sample are found to be less than that of conventional sample. Low dielectric constant is attributed to the low density. Smaller grain size is found to be responsible for low quality factor and the presence of small percentage of TiO2 is observed to achieve the temperature stable resonant frequency.

Surface ionic states and structure of titanate nanotubes

“…This excessively high temperature, although required for crystallization, has caused a complete restructuring of the morphology. Since the dielectric properties and the grain size are interconnected 17 the present results are quite interesting as the average diameter of the ber can be controlled by appropriate choice of the polymer and solvent combination. 10,18 Furthermore, relatively higher diameter (0.5-2 mm) can be achieved by selecting non-polymeric system for electrospinning, 8 which is proven to be compatible in ALD.…”

“…8 Notably the uniformity in the grain size reduces the additional dielectric loss. 17 Nevertheless, in XRD we will see the formation of a well developed polycrystalline Zn 2 TiO 4 . On the other hand, since the ZT13 (Fig.…”