Nonohmic Properties of Zinc Oxide Ceramics

TLDR

The study discusses a possible explanation for nonohmic behavior in ZnO ceramics based on data and a simple model. The authors investigate the nonohmic properties of ZnO ceramics containing five additives (Bi₂O₃, CoO, MnO, Cr₂O₃, Sb₂O₃) as functions of sintering temperature, additive content, and temperature dependence. They examine how sintering temperature, additive concentration, and temperature affect the nonohmic behavior of these ZnO ceramics. Electron microscopy and X‑ray analysis reveal segregation layers at grain boundaries composed of ZnO and the additives, with resistivity ≈10¹³ Ω·cm, dielectric constant ≈170, and a critical electric field of ≈10⁴ V/cm that triggers the steep current rise.

Abstract

Nonohmic properties of ZnO ceramics with five additives of Bi 2 O 3 , CoO, MnO, Cr 2 O 3 , and Sb 2 O 3 are studied in relation to sintering temperature, additive content, and temperature dependence. The observation of electron photomicrographs and X-ray microanalysis proves a ceramic microstructure such that ZnO and these five oxides form, at the grain boundaries, segregation layers which are responsible for the nonohmic properties. The electrical resistivity and dielectric constant of segregation layers are estimated to be 10 13 ohm-cm, and 170, respectively by using a simple model. The electric field strength corresponding to the steep rise in the current is also estimated to be 10 4 V/cm by taking account of the concentration of applied voltage at the segregation layer. In view of these data and simple model, a possible explanation for nonohmic properties is discussed.