Cryogenic microwave dielectric properties of Mg2TiO4ceramics added with CeO2nanoparticles

Abstract

The microwave dielectric properties of <TEX>$CeO_2$</TEX> nanoparticles (0.5, 1.0 & 1.5wt%) doped <TEX>$Mg_2TiO_4$</TEX> (MTO) ceramics have been investigated at cryogenic temperatures. The XRD patterns of the samples were refined using the full proof program reveal the inverse spinel structure without any secondary phases. The addition of <TEX>$CeO_2$</TEX> nanoparticles lowered the sintering temperature with enhancement in density and grain size as compared to pure MTO ceramics. This is attributed to the higher sintering velocity of the fine particles. Further, the microwave dielectric properties of the MTO ceramics were measured at cryogenic temperatures in the temperature range of 6.5-295 K. It is observed that the loss tangent (<TEX>$tan{\delta}$</TEX>) of all the samples increased with temperature. However, the <TEX>$CeO_2$</TEX> nanoparticles doped MTO ceramics manifested lower loss tangents as compared to the pure MTO ceramics. The loss tangents of the pure and MTO ceramics doped with 1.5 wt% of <TEX>$CeO_2$</TEX> nanoparticles measured at 6.5K are found to be <TEX>$6.6{\times}10^{-5}$</TEX> and <TEX>$5.4{\times}10^{-5}$</TEX>, respectively. The addition of <TEX>$CeO_2$</TEX> nanoparticles did not cause any changes on the temperature stability of the MTO ceramics at cryogenic temperatures. On the other hand, the temperature coefficient of the permittivity increased with rise in temperature and with the wt% of <TEX>$CeO_2$</TEX> nanoparticles. The obtained lower loss tangent values at cryogenic temperatures can be attributed to the decrease in both intrinsic and extrinsic losses in the MTO ceramics.