Microstructural, optical, and magnetic properties and specific absorption rate of bismuth ferrite/SiO2 nanoparticles

Abstract

In this study, the microstructural, optical, and magnetic properties and specific absorption rate (SAR) of bismuth ferrite/SiO _2 nanoparticles were successfully investigated. The coprecipitation method was used to synthesize the nanoparticles. X-ray diffraction patterns showed the presence of sillenite-type Bi _25 FeO _40 with a body-centered cubic structure. The crystallite size of Bi _25 FeO _40 was 35.0 nm, which increased to 41.5 nm after SiO _2 encapsulation. Transmission electron microscopy images confirmed that all samples were polycrystalline. The presence of Si–O–Si (siloxane) stretching at 1089 cm ^−1 in Fourier transform infrared spectra confirmed the encapsulation of SiO _2 . Magnetic measurements at room temperature indicated weak ferromagnetic properties of the samples. The coercivity of the bismuth ferrite nanoparticles was 78 Oe, which increased after SiO _2 encapsulation. In contrast, their maximum magnetization, 0.54 emu g ^−1 , reduced after SiO _2 encapsulation. The determined bandgap energy of the bismuth ferrite nanoparticles was approximately 2.1 eV, which increased to 2.7 eV after SiO _2 encapsulation. The effect of SiO _2 encapsulation on the SAR of the samples was investigated using a calorimetric method. The SAR values of the bismuth ferrite nanoparticles were 49, 61, and 84 mW g ^−1 under alternating magnetic field (AMF) strengths of 150, 200, and 250 Oe, respectively, which decreased after SiO _2 encapsulation. The maximum magnetization and the AMF strength influenced the SAR of the nanoparticles. The results showed that SiO _2 has a significant effect in determining the microstructural, optical, and magnetic properties and SAR of the nanoparticles.

Keywords

• bismuth ferrite
• SiO2
• encapsulation
• co-precipitation
• specific absorption rate