Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process
The microstructure and magnetic properties of methane (CH<sub>4</sub>) heat-treated Sr-hexaferrite powders during the re-calcination process were investigated and compared with the magnetic properties of conventionally synthesized Sr-hexaferrite powder. Gradual changes in the magnetic be...
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| Format: | Article |
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MDPI AG
2023-04-01
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| Series: | Magnetochemistry |
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| Online Access: | https://www.mdpi.com/2312-7481/9/4/103 |
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| author | Ramin Dehghan Seyyed Ali Seyyed Ebrahimi Zahra Lalegani Bejan Hamawandi |
| author_facet | Ramin Dehghan Seyyed Ali Seyyed Ebrahimi Zahra Lalegani Bejan Hamawandi |
| author_sort | Ramin Dehghan |
| collection | DOAJ |
| description | The microstructure and magnetic properties of methane (CH<sub>4</sub>) heat-treated Sr-hexaferrite powders during the re-calcination process were investigated and compared with the magnetic properties of conventionally synthesized Sr-hexaferrite powder. Gradual changes in the magnetic behavior of the produced powder in each re-calcination stage were investigated using magnetization curves obtained from the vibration sample magnetometry (VSM) technique. First, the initial Sr-hexaferrite powder was prepared by the conventional route. Then the powder was heat treated in a dynamic CH<sub>4</sub> atmosphere in previously optimized conditions (temperature: 950 °C, gas flow rate:15 cc min<sup>−1</sup> and time: 30 min), and finally, re-calcined in various temperatures from 200 to 1200 °C. By investigating the hysteresis loops, we found the transition temperature of soft to hard magnetic behavior to be 700 °C. The maximum ratio M<sub>r</sub>/M<sub>s</sub> was obtained at temperatures of 800–1100 °C. At 1100 °C, and despite the Sr-hexaferrite single phase, the magnetic behavior showed a multiphase behavior that was demonstrated by a kink in the hysteresis loop. Uniform magnetic behavior was observed only at 900 °C and 1000 °C. Although the ratio M<sub>r</sub>/M<sub>s</sub> was almost the same at these temperatures, the values of M<sub>r</sub> and M<sub>s</sub> at 1000 °C were almost double of 900 °C. At 1000 °C, the second quadrant of hysteresis curve had the maximum area. Therefore, 1000 °C was the optimum temperature for re-calcination after CH<sub>4</sub> gas heat treatment in the optimized conditions. Due to the presence of a small amount of hematite soft phase at 1000 °C, the most probable reason for the exclusive properties of the optimized product may be the exchange coupling phenomenon between the hard Sr-hexaferrite phase and the impurity of the soft hematite phase. |
| first_indexed | 2024-03-11T04:48:11Z |
| format | Article |
| id | doaj.art-0032880a1f1f4d7199e63064e1d6fdc5 |
| institution | Directory Open Access Journal |
| issn | 2312-7481 |
| language | English |
| last_indexed | 2024-03-11T04:48:11Z |
| publishDate | 2023-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Magnetochemistry |
| spelling | doaj.art-0032880a1f1f4d7199e63064e1d6fdc52023-11-17T20:09:44ZengMDPI AGMagnetochemistry2312-74812023-04-019410310.3390/magnetochemistry9040103Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination ProcessRamin Dehghan0Seyyed Ali Seyyed Ebrahimi1Zahra Lalegani2Bejan Hamawandi3Advanced Magnetic Materials Research Center, School of Metallurgy and Materials, University of Tehran, Tehran 11155 4563, IranAdvanced Magnetic Materials Research Center, School of Metallurgy and Materials, University of Tehran, Tehran 11155 4563, IranAdvanced Magnetic Materials Research Center, School of Metallurgy and Materials, University of Tehran, Tehran 11155 4563, IranDepartment of Applied Physics, KTH Royal Institute of Technology, SE-106 91 Stockholm, SwedenThe microstructure and magnetic properties of methane (CH<sub>4</sub>) heat-treated Sr-hexaferrite powders during the re-calcination process were investigated and compared with the magnetic properties of conventionally synthesized Sr-hexaferrite powder. Gradual changes in the magnetic behavior of the produced powder in each re-calcination stage were investigated using magnetization curves obtained from the vibration sample magnetometry (VSM) technique. First, the initial Sr-hexaferrite powder was prepared by the conventional route. Then the powder was heat treated in a dynamic CH<sub>4</sub> atmosphere in previously optimized conditions (temperature: 950 °C, gas flow rate:15 cc min<sup>−1</sup> and time: 30 min), and finally, re-calcined in various temperatures from 200 to 1200 °C. By investigating the hysteresis loops, we found the transition temperature of soft to hard magnetic behavior to be 700 °C. The maximum ratio M<sub>r</sub>/M<sub>s</sub> was obtained at temperatures of 800–1100 °C. At 1100 °C, and despite the Sr-hexaferrite single phase, the magnetic behavior showed a multiphase behavior that was demonstrated by a kink in the hysteresis loop. Uniform magnetic behavior was observed only at 900 °C and 1000 °C. Although the ratio M<sub>r</sub>/M<sub>s</sub> was almost the same at these temperatures, the values of M<sub>r</sub> and M<sub>s</sub> at 1000 °C were almost double of 900 °C. At 1000 °C, the second quadrant of hysteresis curve had the maximum area. Therefore, 1000 °C was the optimum temperature for re-calcination after CH<sub>4</sub> gas heat treatment in the optimized conditions. Due to the presence of a small amount of hematite soft phase at 1000 °C, the most probable reason for the exclusive properties of the optimized product may be the exchange coupling phenomenon between the hard Sr-hexaferrite phase and the impurity of the soft hematite phase.https://www.mdpi.com/2312-7481/9/4/103strontium hexaferriteGTRmagnetic propertiesexchange coupling |
| spellingShingle | Ramin Dehghan Seyyed Ali Seyyed Ebrahimi Zahra Lalegani Bejan Hamawandi Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process Magnetochemistry strontium hexaferrite GTR magnetic properties exchange coupling |
| title | Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process |
| title_full | Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process |
| title_fullStr | Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process |
| title_full_unstemmed | Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process |
| title_short | Investigation of Microstructure and Magnetic Properties of CH<sub>4</sub> Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process |
| title_sort | investigation of microstructure and magnetic properties of ch sub 4 sub heat treated sr hexaferrite powders during re calcination process |
| topic | strontium hexaferrite GTR magnetic properties exchange coupling |
| url | https://www.mdpi.com/2312-7481/9/4/103 |
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