Effect Milling Time on the Phase Formation and Magnetic Properties of Co0.75Ni0.25Ti0.975Y0.025O3 Sintered at 1000 C
Tesalonika Siregar (a,b), Yunasfi (b), Mashadi (b), Wisnu Ari Adi (b), Budhy Kurniawan (a*), Jan Setiawan (b*)

a) Departement of Physics, Universitas Indonesia, Depok 16424, Indonesia
b)Research Center for Advanced Material-National Research and Innovation Agency (BRIN), Complex Puspiptek Building 440-442, Tangerang South, Banten 15314, Indonesia
* budhy.kurniawan[at]sci.ui.ac.id, *jans002[at]brin.go.id

Abstract

This study investigates the effect of milling time on the phase formation and magnetic properties of Co0.75Ni0.25Ti0.975Y0.025O3 (CNTYO) synthesized via a solid-state reaction method and sintered at 1000 C. Stoichiometric amounts of Co3O4, NiO, TiO2, and Y2O3 powders were mixed and milled using High Energy Milling at 1000 rpm for 1, 3, 5, and 7 hours. X-ray diffraction (XRD) analysis revealed that a single-phase trigonal structure was fully formed after 5 hours of milling, while Y2O3 residues were still detected at 3 hours. Lattice parameter analysis confirmed structural stability with slight variations in unit cell volume and microstrain. Crystallite size calculated using the Williamson-Hall method decreased from 1021 nm (1 hour) to 862 nm (7 hours), accompanied by a reduction in microstrain from 9.5 x 10^-4 to 8.1 x 10^-4. Scanning Electron Microscopy (SEM) observations supported these findings, showing decreased grain size and improved homogeneity with prolonged milling time. The correlation between XRD, WH plot, and SEM results indicates that extended milling enhances densification and structural refinement. Magnetic measurements using a Vibrating Sample Magnetometer (VSM) demonstrated a decrease in saturation magnetization (Ms) from 0.569 emu/g to 0.541 emu/g and a reduction in coercivity (Hc) from 0.0103 Oe to 0.0020 Oe with increasing milling time. These reductions are attributed to weakened magnetic domain interactions caused by crystallite refinement and increased grain boundary area, which hinder domain wall movement. Overall, a milling time of 5 hours provides an optimal balance between phase formation, crystal structure stability, microstructural refinement, and controlled magnetic behavior.

Keywords: High energy milling- Phase Formation- Williamson-Hall method- Microstructure- Magnetic properties

Topic: Material Physics