Hydrothermal synthesis of SrFe12O19 nanoparticles: Effect of the choice of base and base concentration

Jennifer Hoelscher; Anna Zink Eikeland; Mogens Christensen

doi:10.1088/1361-6463/abd2ec

Hydrothermal synthesis of SrFe₁₂O₁₉ nanoparticles: Effect of the choice of base and base concentration

Jennifer Hoelscher, Anna Zink Eikeland, Mogens Christensen^*

^*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

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Abstract

Platelet shaped strontium hexaferrite (SrFe ₁₂O ₁₉) crystallites were hydrothermally synthesized in an autoclave to study the effect of (a) Fe/Sr molar ratio, (b) choice of base NaOH/KOH and (c) base concentration. The influence of these parameters on the final product is evaluated with regards to phase composition, structure and magnetic properties. Rietveld refinements were performed on powder x-ray diffraction (PXRD) data to determine the phase composition, structural changes, crystallite sizes, and preferred orientation, while the magnetic properties were measured using a vibrating sample magnetometer. When NaOH is used as the base, the samples consist mostly (>95 wt.%) of SrFe ₁₂O ₁₉ up to the same molar ratio of Fe/Sr = 8, independent of the concentration of the base. In contrast, when using KOH, the phase composition depends on both the molar ratio of Fe/Sr and the concentration of KOH. High concentrations of Sr ²⁺ and OH ^- (Fe/Sr = 1 and OH ^-/NO ₃ ^- = 4) result in the growth of wide crystallites (>400 nm). The thickness of the crystallites are in all cases around 40 nm causing the crystallites to have an anisotropic shape, which can align without applying an external magnetic field. In the case of KOH as base instead of NaOH, an expansion of the unit cell is observed, which can be attributed to K ⁺ substituting Sr ²⁺ in the structure. This is corroborated by increasing microstrain when increasing the KOH/NO ₃ ^- ratio. Variations in the observed coercivity may be attributed to substitution of Sr ²⁺ by K ⁺. The present study illustrates that meticulous control of all reaction parameters and a meticulous analysis of the crystal structure is key for preparing and understanding hard-magnetic SrFe ₁₂O ₁₉

Original language	English
Article number	134004
Journal	Journal of Physics D: Applied Physics
Volume	54
Issue	13
Number of pages	15
ISSN	0022-3727
DOIs	https://doi.org/10.1088/1361-6463/abd2ec
Publication status	Published - Apr 2021

Keywords

Autoclave synthesis
Hexaferrites
Magnetic properties
Nanoparticles
Powder x-ray diffraction
PERFORMANCE
powder x-ray diffraction
FERRITES
SYNCHROTRON X-RAY
autoclave synthesis
hexaferrites
FERRIHYDRITE
magnetic properties
nanoparticles
ORIENTATION
HEXAFERRITE
MAGNETIC-PROPERTIES
MORPHOLOGY

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10.1088/1361-6463/abd2ec

Hydrothermal synthesis of SrFe12O19 nanoparticles effect of the choice of base and base concentrationAccepted manuscript, 1.33 MBLicence: CC BY-NC-ND

Cite this

@article{1f136490fd4547b8ad9cdd64a8e0b33d,

title = "Hydrothermal synthesis of SrFe12O19 nanoparticles: Effect of the choice of base and base concentration",

abstract = "Platelet shaped strontium hexaferrite (SrFe 12O 19) crystallites were hydrothermally synthesized in an autoclave to study the effect of (a) Fe/Sr molar ratio, (b) choice of base NaOH/KOH and (c) base concentration. The influence of these parameters on the final product is evaluated with regards to phase composition, structure and magnetic properties. Rietveld refinements were performed on powder x-ray diffraction (PXRD) data to determine the phase composition, structural changes, crystallite sizes, and preferred orientation, while the magnetic properties were measured using a vibrating sample magnetometer. When NaOH is used as the base, the samples consist mostly (>95 wt.%) of SrFe 12O 19 up to the same molar ratio of Fe/Sr = 8, independent of the concentration of the base. In contrast, when using KOH, the phase composition depends on both the molar ratio of Fe/Sr and the concentration of KOH. High concentrations of Sr 2+ and OH - (Fe/Sr = 1 and OH -/NO 3 - = 4) result in the growth of wide crystallites (>400 nm). The thickness of the crystallites are in all cases around 40 nm causing the crystallites to have an anisotropic shape, which can align without applying an external magnetic field. In the case of KOH as base instead of NaOH, an expansion of the unit cell is observed, which can be attributed to K + substituting Sr 2+ in the structure. This is corroborated by increasing microstrain when increasing the KOH/NO 3 - ratio. Variations in the observed coercivity may be attributed to substitution of Sr 2+ by K +. The present study illustrates that meticulous control of all reaction parameters and a meticulous analysis of the crystal structure is key for preparing and understanding hard-magnetic SrFe 12O 19 ",

keywords = "Autoclave synthesis, Hexaferrites, Magnetic properties, Nanoparticles, Powder x-ray diffraction, PERFORMANCE, powder x-ray diffraction, FERRITES, SYNCHROTRON X-RAY, autoclave synthesis, hexaferrites, FERRIHYDRITE, magnetic properties, nanoparticles, ORIENTATION, HEXAFERRITE, MAGNETIC-PROPERTIES, MORPHOLOGY",

author = "Jennifer Hoelscher and Eikeland, {Anna Zink} and Mogens Christensen",

year = "2021",

month = apr,

doi = "10.1088/1361-6463/abd2ec",

language = "English",

volume = "54",

journal = "Journal of Physics D: Applied Physics",

issn = "0022-3727",

publisher = "IOP Publishing Ltd.",

number = "13",

}

Hydrothermal synthesis of SrFe₁₂O₁₉ nanoparticles: Effect of the choice of base and base concentration. / Hoelscher, Jennifer; Eikeland, Anna Zink; Christensen, Mogens.
In: Journal of Physics D: Applied Physics, Vol. 54, No. 13, 134004, 04.2021.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Hydrothermal synthesis of SrFe12O19 nanoparticles

T2 - Effect of the choice of base and base concentration

AU - Hoelscher, Jennifer

AU - Eikeland, Anna Zink

AU - Christensen, Mogens

PY - 2021/4

Y1 - 2021/4

N2 - Platelet shaped strontium hexaferrite (SrFe 12O 19) crystallites were hydrothermally synthesized in an autoclave to study the effect of (a) Fe/Sr molar ratio, (b) choice of base NaOH/KOH and (c) base concentration. The influence of these parameters on the final product is evaluated with regards to phase composition, structure and magnetic properties. Rietveld refinements were performed on powder x-ray diffraction (PXRD) data to determine the phase composition, structural changes, crystallite sizes, and preferred orientation, while the magnetic properties were measured using a vibrating sample magnetometer. When NaOH is used as the base, the samples consist mostly (>95 wt.%) of SrFe 12O 19 up to the same molar ratio of Fe/Sr = 8, independent of the concentration of the base. In contrast, when using KOH, the phase composition depends on both the molar ratio of Fe/Sr and the concentration of KOH. High concentrations of Sr 2+ and OH - (Fe/Sr = 1 and OH -/NO 3 - = 4) result in the growth of wide crystallites (>400 nm). The thickness of the crystallites are in all cases around 40 nm causing the crystallites to have an anisotropic shape, which can align without applying an external magnetic field. In the case of KOH as base instead of NaOH, an expansion of the unit cell is observed, which can be attributed to K + substituting Sr 2+ in the structure. This is corroborated by increasing microstrain when increasing the KOH/NO 3 - ratio. Variations in the observed coercivity may be attributed to substitution of Sr 2+ by K +. The present study illustrates that meticulous control of all reaction parameters and a meticulous analysis of the crystal structure is key for preparing and understanding hard-magnetic SrFe 12O 19

AB - Platelet shaped strontium hexaferrite (SrFe 12O 19) crystallites were hydrothermally synthesized in an autoclave to study the effect of (a) Fe/Sr molar ratio, (b) choice of base NaOH/KOH and (c) base concentration. The influence of these parameters on the final product is evaluated with regards to phase composition, structure and magnetic properties. Rietveld refinements were performed on powder x-ray diffraction (PXRD) data to determine the phase composition, structural changes, crystallite sizes, and preferred orientation, while the magnetic properties were measured using a vibrating sample magnetometer. When NaOH is used as the base, the samples consist mostly (>95 wt.%) of SrFe 12O 19 up to the same molar ratio of Fe/Sr = 8, independent of the concentration of the base. In contrast, when using KOH, the phase composition depends on both the molar ratio of Fe/Sr and the concentration of KOH. High concentrations of Sr 2+ and OH - (Fe/Sr = 1 and OH -/NO 3 - = 4) result in the growth of wide crystallites (>400 nm). The thickness of the crystallites are in all cases around 40 nm causing the crystallites to have an anisotropic shape, which can align without applying an external magnetic field. In the case of KOH as base instead of NaOH, an expansion of the unit cell is observed, which can be attributed to K + substituting Sr 2+ in the structure. This is corroborated by increasing microstrain when increasing the KOH/NO 3 - ratio. Variations in the observed coercivity may be attributed to substitution of Sr 2+ by K +. The present study illustrates that meticulous control of all reaction parameters and a meticulous analysis of the crystal structure is key for preparing and understanding hard-magnetic SrFe 12O 19

KW - Autoclave synthesis

KW - Hexaferrites

KW - Magnetic properties

KW - Nanoparticles

KW - Powder x-ray diffraction

KW - PERFORMANCE

KW - powder x-ray diffraction

KW - FERRITES

KW - SYNCHROTRON X-RAY

KW - autoclave synthesis

KW - hexaferrites

KW - FERRIHYDRITE

KW - magnetic properties

KW - nanoparticles

KW - ORIENTATION

KW - HEXAFERRITE

KW - MAGNETIC-PROPERTIES

KW - MORPHOLOGY

U2 - 10.1088/1361-6463/abd2ec

DO - 10.1088/1361-6463/abd2ec

M3 - Journal article

SN - 0022-3727

VL - 54

JO - Journal of Physics D: Applied Physics

JF - Journal of Physics D: Applied Physics

IS - 13

M1 - 134004

ER -