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<p>Modification of lithium spinel ferrite (Li<sub>0.5</sub>Fe<sub>2.5</sub>O<sub>4</sub>) with rare-earth elements, leading to changes in magnetic and electrical properties, plays an important role in the development of thermally stable microwave ferrites. For this purpose, lithium ferrite was prepared from Fe<sub>2</sub>O<sub>3</sub>/Li<sub>2</sub>CO<sub>3</sub>/La(OH)<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub>/Li<sub>2</sub>CO<sub>3</sub>/La<sub>2</sub>O<sub>3</sub> reagent mixtures using a two-step ceramic method involving preliminary solid-phase synthesis at 900&#xa0;°C and sintering at 1100 and 1150&#xa0;°C. The formation and properties of ferrites were studied using thermogravimetry, differential scanning calorimetry, dilatometry, X-ray diffraction, Mössbauer spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, hysteresis loops and DC conductivity measurements. It was found that the composite Li<sub>0.5</sub>Fe<sub>2.5</sub>O<sub>4</sub> (82–85 mass%)–LaFeO<sub>3</sub> (15–18 mass%) was formed, the density of which increased from 3.93–4.01 to 4.54–4.56&#xa0;g&#xa0;cm<sup>−3</sup>, and the porosity decreased from 18.0–18.8 to 2.9–3.1% with an increase in sintering temperature. The formation of unsubstituted lithium ferrite determined the high Curie temperature of the composites, equal to 629.5–632&#xa0;°C. The samples exhibited high saturation magnetization (47.8–49.8&#xa0;emu&#xa0;g<sup>−1</sup>) and low coercivity (21–27&#xa0;Oe). The dense composite sintered at 1150&#xa0;°C and obtained using La(OH)<sub>3</sub> was characterized by a higher electrical resistivity of up to 8 × 10<sup>7</sup>&#xa0;Ω&#xa0;cm compared to that prepared from La<sub>2</sub>O<sub>3</sub> (4 × 10<sup>7</sup>&#xa0;Ω&#xa0;cm), which is a consequence of the different morphology of LaFeO<sub>3</sub> grains. These excellent performances highlight the promising prospects for the application of lanthanum-modified lithium ferrites in microwave devices.</p> Graphical abstract <p></p>

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Thermal analysis of synthesis and electromagnetic properties of La-modified lithium ferrites

  • 期刊论文

  • 发表日期：

    2026年7月6日

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  • Yulia S. Elkina,
  • Elena N. Lysenko,
  • Vitaliy A. Vlasov,
  • Anatoliy P. Surzhikov,
  • Vladimir D. Elkin,
  • Yurii V. Knyazev

摘要

Modification of lithium spinel ferrite (Li0.5Fe2.5O4) with rare-earth elements, leading to changes in magnetic and electrical properties, plays an important role in the development of thermally stable microwave ferrites. For this purpose, lithium ferrite was prepared from Fe2O3/Li2CO3/La(OH)3 and Fe2O3/Li2CO3/La2O3 reagent mixtures using a two-step ceramic method involving preliminary solid-phase synthesis at 900 °C and sintering at 1100 and 1150 °C. The formation and properties of ferrites were studied using thermogravimetry, differential scanning calorimetry, dilatometry, X-ray diffraction, Mössbauer spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, hysteresis loops and DC conductivity measurements. It was found that the composite Li0.5Fe2.5O4 (82–85 mass%)–LaFeO3 (15–18 mass%) was formed, the density of which increased from 3.93–4.01 to 4.54–4.56 g cm−3, and the porosity decreased from 18.0–18.8 to 2.9–3.1% with an increase in sintering temperature. The formation of unsubstituted lithium ferrite determined the high Curie temperature of the composites, equal to 629.5–632 °C. The samples exhibited high saturation magnetization (47.8–49.8 emu g−1) and low coercivity (21–27 Oe). The dense composite sintered at 1150 °C and obtained using La(OH)3 was characterized by a higher electrical resistivity of up to 8 × 107 Ω cm compared to that prepared from La2O3 (4 × 107 Ω cm), which is a consequence of the different morphology of LaFeO3 grains. These excellent performances highlight the promising prospects for the application of lanthanum-modified lithium ferrites in microwave devices.

Graphical abstract