The formation of precipitates in the system

¹ Research Center for Dielectric and Advanced Matter Physics (RCDAMP) Pusan National University - Busan 609-735, Korea
² Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH) - Pohang 790-784, Korea
³ Busan Center, Korea Basic Science Institute (KBSI) - Busan 609-735, Korea
⁴ School of Nano-Science and Technology, Pusan National University Busan 609-735, Korea

Corresponding author: syjeong@pusan.ac.kr

Received: 11 March 2005
Accepted: 26 July 2005

Abstract

Magnetic matter such as transition metals or metal oxides are able to exhibit ferromagnetism by the clustering in magnetic semiconductors. We fabricated Co-doped ZnO samples using the sol-gel method, and studied the magnetic precipitates in the samples by using both neutron diffraction and X-ray absorption fine-structure measurements. The structural details were characterized by X-ray and neutron diffraction, and the data were interpreted using Rietveld refinement. The doped Co ion was fully substituted into a ZnO lattice at 5, but the secondary phase of the Co₃O₄ was formed above 5 of Co doping and its neutron diffraction signal increased up to 20. The quantitative amounts of each phase were calculated to be 55.43 of Co₃O₄ and 44.57 of fully cobalt-substituted ZnO. In the 30 Co-doped sample, Co metal, as well as oxidized Co, were identified in this study. Those signals, however, were not observed by X-ray diffraction. To verify the local chemical bonding state, we used extended X-ray absorption fine-structure measurement and investigated the formation of precipitates by calculating the inter-atomic distance using Fourier analysis.