PENGARUH KONSENTRASI Zn DAN SUHU ANNEALING TERHADAP STRUKTUR KRISTAL DAN SIFAT KEMAGNETAN NANOPARTIKEL Co1-xZnxFe2O4

HERI KISWANTO, Dr. Edi Suharyadi, M.Eng

2018 | Tesis | MAGISTER FISIKA

Sampel Co1-xZnxFe2O4 telah berhasil disintesis dengan metode co-presipitasi dan di-annealing pada suhu yang berbeda, yaitu 400 C, 600 C, 800 C dan 1000 C selama 2 jam. Ukuran kristalit diestimasi dengan metode Scherrer yang ditemukan menurun dari 9,1 hingga 11,2 nm dengan meningkatknya konsentrasi Zn. Peningkatan suhu annealing meningkatkan ukuran kristalit dari 13,4 - 39,2 nm karena adanya pertumbuhan butir. Parameter kisi ditemukan meningkat dari 8,18 - 8,25 A. akibat subtitusi Zn yang memiliki radius ionik lebih besar. Spektra FTIR mengkonfirmasi adanya vibrasi stretching pada bilangan gelombang di sekitar 478 dan 586 cm-1 pada site tetrahedral dan oktahedral. Baik koersivitas (Hc) maupun magnetisasi saturasi (Ms) menurun masing-masing dari 34 - 20 emu/g dan 674 - 158 Oe, dengan meningkatnya konsentrasi Zn. Sedangkan Ms dan Hc masing-masing meningkat dari 51 - 191 emu/g dan 150 - 250 Oe dengan meningkatnya suhu annealing. Hal ini dapat dikorelasikan karena adanya pertumbuhan butir serta perubahan mikrostruktur selama annealing. Citra TEM juga menjukkan bahwa mikrostruktur dan morfologi nanopartikel berubah secara signifikan pasca annealing. Konsentrasi Zn pada x=0,4 dan annealing pada suhu 1000 C memberikan hasil optimum pada nilai Ms dan Hc nanopartikel Co1-xZnxFe2O4.

Co1-xZnxFe2O4 nanoparticles have been successfully synthesized by co-precipitation method and annealed at different temperatures, i.e. 400 C, 600 C, 800 C and 1000 C for 2 hours. Both XRD and FTIR analyses confirm the formation of cubic spinel phase. The crystallite sizes of nanoparticles was calculated by using Scherrer's formula and found decreased from 9.1 to 11.2 nm by increasing Zn concentration. Increasing annealing temperature gave larger crystallite size ranging from 13.4 to 39.2 nm due to the grain growth of nanoparticles because of thermal treatment. The increase in lattice parameter from 8.17 to 8.21 A by increasing zinc content as a result of the different ionic radii. The Fourier transform infrared spectroscope (FTIR) spectra also confirmed the existence of symmetric stretching vibration bands of metal ions around 478 and 586 cm-1 in tetrahedral and octahedral sites, respectively. Both coercivity (Hc) and magnetization saturation (Ms) decreased monotonically for as-prepared samples with the increase in Zn concentration. The Ms and the Hc decrease from 34.3 to 20.3 emu/g and 674 to 158 Oe respectively, by increasing zinc concentration. While the annealed samples showed that Ms and Hc were observed to be enhanced with the increase in annealing. The Ms increased from 51 to 91 emu/g and the Hc increased from 150 to 250 Oe by increasing annealing temperature. This could be understood due to the redistribution of cations migrated to their site of preference and the change of microstructural after annealing. The transmission electron microscope (TEM) image revealed that the microstructure and morphology of nanoparticles were change after annealing. Finally, sample with x=04 and annelaed at 1000C has the optimum value of Hc ad Ms of the sample Co1-xZnxFe2O4 nanoparticles.

Kata Kunci : konsentrasi Zn, suhu annealing, struktur kristal sifat kemagnetan/ Zn concentration, annealing temperature, crystal structure, magnetic properties