Speaker
Description
Due to their high potential for use in ceramic capacitors, high–performance giant dielectric properties (HP–GDPs), i.e., high dielectric constant (ɛʹ), low loss tangent (tan$\delta$), and the temperature stability of ɛʹ over a wide temperature range (Δɛʹ/ɛʹ$_{25}$(%)) < $\pm 15$, of acceptor/donor (A/D) codoped–$TiO_{2}$ ceramics have been widely studied since the discovery of a new $In^{3+}$/$Nb^{5+}$ codoped rutile–$TiO_{2}$. In this presentation, HP–GDPs of the $TiO_{2}$–based oxides were achieved in $Sn^{4+}/Nb^{5+}$ codoped rutile $TiO_{2}$ (SnNTO) ceramics. $SnO_{2}$ isovalent ($I^{4+}$) dopant was employed to replace the A dopants. The SnNTO samples with different $Sn^{4+}/Nb^{5+}$ concentrations (x = 0.01–0.05) were prepared using a standard solid–state reaction (SSR) method . The X–ray diffraction patterns of all the SnNTO ceramics showed only a single–phase rutile–$TiO_{2}$ (JCPS 21–1276) without any impurity phases. A highly dense microstructure of all SnNTO samples consisted of grains and grain boundaries. The average grain size slightly enlarged from 1.6 to 2.6 µm, which was caused by the diffusion of oxygen vacancies ($V_{o}^{••}$) due to the existence of multivalent $Sn^{2+}/Sn^{4+}$ ions. The dielectric properties of the SnNTO ceramics showed a high ɛʹ (~$10^{4}$), very low tan$\delta$ (<~0.05), and a low Δɛʹ/ɛʹ$_{25}$(%) < $\pm 15$ values in a wide temperature range. The origin of HP–GDPs was investigated using impedance spectroscopy (IS). The dielectric response was described by Maxwell–Wagner relaxation.
Keywords: $TiO_{2}$; Giant dielectric constant; Codopant; Grain boundary; Maxwell–Wagner relaxation
