Control of coring effect in BaTi4O9 microwave dielectric ceramics by doping with Mn4+

In the present work, we have attempted to reduce the effect of coring effect in the titanate ceramic system BaTi4O9 (BT4) by doping it with Mn4+. The microwave dielectric BaTi4O9 ceramics doped with 0, 0.5 and 1.0 mol% Mn4+ were synthesized by conventional ceramic processing route. The XRD studies confirmed a single phase crystalline structure for all the ceramic samples studied. The SEM micrographs of the ceramics reveal a microstructural change leading towards a more uniform grain size distribution as the Mn4+ content increases to 1.0 mol%. In the low frequency region (100 Hz to 1 MHz), the temperature stability of dielectric properties exhibits a marked improvement with the increasing amount of Mn4+ in the ceramic system. In the microwave frequency region (9.3 GHz), Q-factor increases from 11,625 GHz to 46,500 GHz for BaTi4O9 ceramic doped with 1.0 mol% Mn4+. The present paper reveals that the commonly observed degradation of dielectric properties due to coring effect in the BaTi4O9 ceramic system can be controlled by doping it with an appropriate quantity of Mn4+.