Ni를 첨가한 ZnO-Bi2O3-Sb2O3계의 소결과 전기적 특성

Abstract

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of <TEX>$ZnO-Bi_2O_3-Sb_2O_3$</TEX> (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore (<TEX>$Zn_2Bi_3Sb_3O_{14}$</TEX>) was decomposed more than <TEX>$100^{\circ}C$</TEX> lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of <TEX>$Zn_7Sb_2O_{12}$</TEX> spinel (<TEX>$\alpha$</TEX> and <TEX>$\beta$</TEX>), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than <TEX>$Sb/Bi{\geq}1.0$</TEX> composed of <TEX>$\beta$</TEX>-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient <TEX>$\alpha\;=\;6{\sim}11$</TEX>) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form <TEX>${V_0}^{\cdot}$</TEX> (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.