Fabrication and characterizations of Zn_1−xCo_xO bulk ceramics prepared by solid state reaction combined with spark plasma sintering

Abstract

Zn_1−xCo_xO (x = 0.01, 0.05 and 0.1) bulk ceramics were prepared through a two-step, solid state reaction method combined with spark plasma sintering technique. The single phase Zn_1−xCo_xO powders were synthesized using ZnO and Co₃O₄ at 935 °C in air for 3 h. The Zn_1−xCo_xO bulks were prepared at sintering temperature from 900 to 1,100 °C for 5 min by SPS. The relative density of Zn_1−xCo_xO bulk ceramics sintered at 1,100 °C is higher than 99% of the theoretical value. The Structure, composition analysis, optical absorption, Raman and XPS measurements revealed that the Co²⁺ substituted Zn²⁺ ions and was incorporated into the lattice of ZnO in both of the single phase Zn_1−xCo_xO powders and bulk ceramics. Room- and low-temperature magnetization measurements reveal a paramagnetic behavior and that the paramagnetic Co amount is smaller than the nominal Co concentration for all of Zn_1−xCo_xO samples at 4 K. The paramagnetic magnetism of bulk ceramics is apparently larger than that of powders with the same composition. The electrical properties measurements reveal that the Co concentration has a slight influence on the electrical properties of Zn_1−xCo_xO bulk ceramics. The carriers concentration is about 1 × 10²⁰ cm⁻³ and with the Co concentration increases the resistivity slightly increases from 3.56 × 10⁻³ (x = 0.01) to 5.58 × 10⁻³ (x = 0.1) Ωcm.