Effects of Dy2O3 on the Electrical Properties of a (Nb2O5-Dy2O3-SiO2) Co-doped TiO2 Varistor

Rutile-TiO2 ceramics are very promising electronic ceramic materials which can be applied in varistors because of their good electrical properties. In this work, Dy2O3 was used to improve the electrical properties of a TiO2 varistor doped with 0.60 mol.% Nb2O5 and 0.30 mol.% SiO2. Results showed that the TiO2 varistor doped with 0.30 mol.% Dy2O3 possessed optimal electrical properties with good nonlinear coefficient (α=5.7\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \alpha = 5.7 $$\end{document}), very low breakdown voltage (EB=1.34Vmm-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ E_{\text{B}} = 1.34\;{\text{V}}\,{\text{mm}}^{ - 1} $$\end{document}) and colossal dielectric constant (εr=8.01×105\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \varepsilon_{\text{r}} = 8.01 \times 10^{5} $$\end{document}). The microstructural analysis showed that after the incorporation of Dy2O3 into the TiO2 varistor, the grains tended to be more semiconducting due to the defect carriers derived from the substitution of Dy3+ for Ti4+. Meanwhile, the moderate dopant of Dy2O3 also increased the grain size and narrow grain boundary. Consequently, the breakdown voltage decreased, while the nonlinear coefficient and dielectric constant improved.