Defect states and room temperature ferromagnetism in cerium oxide nanopowders prepared by decomposition of Ce-propionate

V. Mihalache*, J. C. Grivel, M. Secu

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Four batches of cerium oxide powders (with nanocrystallite size of 6.9 nm–572 nm) were prepared from four precursor nanopowders by thermal decomposition of Ce-propionate and annealing in air between 250 °C–1200 °C for 10 min–240 min. Ceria formation reactions, structure, vibrational, luminescence and magnetic properties were investigated by differential scanning calorimetry, x-ray diffraction, electron microscopy, infrared spectroscopy, photoluminescence and SQUID. All the samples exhibit room temperature ferromagnetism, RTFM, (with coercivity, Hc, of 8 Oe - 121 Oe and saturation magnetization, Ms, of up to 6.7*10−3 emu/g) and a broad defect-related photoluminescence, PL, emission in the visible range. The samples derived from the same precursor show Ms proportional to the peak area of defect-related PL emission whereas this is not valid for the samples derived from the different precursors. An improvement of ferromagnetism and intensity of defect-related PL emission was observed when annealing the products in which nanocrystalline cerium oxide coexists with Ce - oxicarbonate traces, Ce2O2CO3. The experimental results were explained based on the following considerations: room temperature ferromagnetism was induced by the defective ceria with high concentration of oxygen vacancies generated by decomposition of Ce-propionate; oxygen vacancies of the starting precursor nanopowders could be redistributed (at the surfaces/grain boundaries, GBs) upon heating under conditions that promote an inert local environment; the decomposition of Ce2O2CO3 residues can provide an excess of oxygen vacancies at the nanoparticles surfaces or GBs, which can induce or enhance ferromagnetism; surfaces/GBs rather than bulk defects appear responsible for RTFM – this can explain the (often reported in literature) inconsistency between oxygen vacancies concentration and Ms.
Original languageEnglish
JournalMaterials Chemistry and Physics
Volume209
Pages (from-to)121-133
ISSN0254-0584
DOIs
Publication statusPublished - 2018

Keywords

  • Cerium oxide nanopowders
  • Ce - propionate
  • Ce2 O2 CO3
  • Ferromagnetism
  • Photoluminescence

Cite this

@article{0c4ce04758584cb08c51c067a94edc4e,
title = "Defect states and room temperature ferromagnetism in cerium oxide nanopowders prepared by decomposition of Ce-propionate",
abstract = "Four batches of cerium oxide powders (with nanocrystallite size of 6.9 nm–572 nm) were prepared from four precursor nanopowders by thermal decomposition of Ce-propionate and annealing in air between 250 °C–1200 °C for 10 min–240 min. Ceria formation reactions, structure, vibrational, luminescence and magnetic properties were investigated by differential scanning calorimetry, x-ray diffraction, electron microscopy, infrared spectroscopy, photoluminescence and SQUID. All the samples exhibit room temperature ferromagnetism, RTFM, (with coercivity, Hc, of 8 Oe - 121 Oe and saturation magnetization, Ms, of up to 6.7*10−3 emu/g) and a broad defect-related photoluminescence, PL, emission in the visible range. The samples derived from the same precursor show Ms proportional to the peak area of defect-related PL emission whereas this is not valid for the samples derived from the different precursors. An improvement of ferromagnetism and intensity of defect-related PL emission was observed when annealing the products in which nanocrystalline cerium oxide coexists with Ce - oxicarbonate traces, Ce2O2CO3. The experimental results were explained based on the following considerations: room temperature ferromagnetism was induced by the defective ceria with high concentration of oxygen vacancies generated by decomposition of Ce-propionate; oxygen vacancies of the starting precursor nanopowders could be redistributed (at the surfaces/grain boundaries, GBs) upon heating under conditions that promote an inert local environment; the decomposition of Ce2O2CO3 residues can provide an excess of oxygen vacancies at the nanoparticles surfaces or GBs, which can induce or enhance ferromagnetism; surfaces/GBs rather than bulk defects appear responsible for RTFM – this can explain the (often reported in literature) inconsistency between oxygen vacancies concentration and Ms.",
keywords = "Cerium oxide nanopowders, Ce - propionate, Ce2 O2 CO3, Ferromagnetism, Photoluminescence",
author = "V. Mihalache and Grivel, {J. C.} and M. Secu",
year = "2018",
doi = "10.1016/j.matchemphys.2018.01.053",
language = "English",
volume = "209",
pages = "121--133",
journal = "Materials Chemistry and Physics",
issn = "0254-0584",
publisher = "Elsevier",

}

Defect states and room temperature ferromagnetism in cerium oxide nanopowders prepared by decomposition of Ce-propionate. / Mihalache, V. ; Grivel, J. C.; Secu, M.

In: Materials Chemistry and Physics, Vol. 209, 2018, p. 121-133.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Defect states and room temperature ferromagnetism in cerium oxide nanopowders prepared by decomposition of Ce-propionate

AU - Mihalache, V.

AU - Grivel, J. C.

AU - Secu, M.

PY - 2018

Y1 - 2018

N2 - Four batches of cerium oxide powders (with nanocrystallite size of 6.9 nm–572 nm) were prepared from four precursor nanopowders by thermal decomposition of Ce-propionate and annealing in air between 250 °C–1200 °C for 10 min–240 min. Ceria formation reactions, structure, vibrational, luminescence and magnetic properties were investigated by differential scanning calorimetry, x-ray diffraction, electron microscopy, infrared spectroscopy, photoluminescence and SQUID. All the samples exhibit room temperature ferromagnetism, RTFM, (with coercivity, Hc, of 8 Oe - 121 Oe and saturation magnetization, Ms, of up to 6.7*10−3 emu/g) and a broad defect-related photoluminescence, PL, emission in the visible range. The samples derived from the same precursor show Ms proportional to the peak area of defect-related PL emission whereas this is not valid for the samples derived from the different precursors. An improvement of ferromagnetism and intensity of defect-related PL emission was observed when annealing the products in which nanocrystalline cerium oxide coexists with Ce - oxicarbonate traces, Ce2O2CO3. The experimental results were explained based on the following considerations: room temperature ferromagnetism was induced by the defective ceria with high concentration of oxygen vacancies generated by decomposition of Ce-propionate; oxygen vacancies of the starting precursor nanopowders could be redistributed (at the surfaces/grain boundaries, GBs) upon heating under conditions that promote an inert local environment; the decomposition of Ce2O2CO3 residues can provide an excess of oxygen vacancies at the nanoparticles surfaces or GBs, which can induce or enhance ferromagnetism; surfaces/GBs rather than bulk defects appear responsible for RTFM – this can explain the (often reported in literature) inconsistency between oxygen vacancies concentration and Ms.

AB - Four batches of cerium oxide powders (with nanocrystallite size of 6.9 nm–572 nm) were prepared from four precursor nanopowders by thermal decomposition of Ce-propionate and annealing in air between 250 °C–1200 °C for 10 min–240 min. Ceria formation reactions, structure, vibrational, luminescence and magnetic properties were investigated by differential scanning calorimetry, x-ray diffraction, electron microscopy, infrared spectroscopy, photoluminescence and SQUID. All the samples exhibit room temperature ferromagnetism, RTFM, (with coercivity, Hc, of 8 Oe - 121 Oe and saturation magnetization, Ms, of up to 6.7*10−3 emu/g) and a broad defect-related photoluminescence, PL, emission in the visible range. The samples derived from the same precursor show Ms proportional to the peak area of defect-related PL emission whereas this is not valid for the samples derived from the different precursors. An improvement of ferromagnetism and intensity of defect-related PL emission was observed when annealing the products in which nanocrystalline cerium oxide coexists with Ce - oxicarbonate traces, Ce2O2CO3. The experimental results were explained based on the following considerations: room temperature ferromagnetism was induced by the defective ceria with high concentration of oxygen vacancies generated by decomposition of Ce-propionate; oxygen vacancies of the starting precursor nanopowders could be redistributed (at the surfaces/grain boundaries, GBs) upon heating under conditions that promote an inert local environment; the decomposition of Ce2O2CO3 residues can provide an excess of oxygen vacancies at the nanoparticles surfaces or GBs, which can induce or enhance ferromagnetism; surfaces/GBs rather than bulk defects appear responsible for RTFM – this can explain the (often reported in literature) inconsistency between oxygen vacancies concentration and Ms.

KW - Cerium oxide nanopowders

KW - Ce - propionate

KW - Ce2 O2 CO3

KW - Ferromagnetism

KW - Photoluminescence

U2 - 10.1016/j.matchemphys.2018.01.053

DO - 10.1016/j.matchemphys.2018.01.053

M3 - Journal article

VL - 209

SP - 121

EP - 133

JO - Materials Chemistry and Physics

JF - Materials Chemistry and Physics

SN - 0254-0584

ER -