Co-precipitation method followed by ultrafast sonochemical synthesis of aluminium doped M type BaFe11.4-xAlxCo0.6O19 hexaferrites for various applications

Abstract

The co-precipitation method followed by Sonochemical process was used to synthesize M-type BaFe11.4-xAlxCo0.6O19 hexaferrites (x = 0.0, 0.4, 0.8, 1.2, and 1.6) with Al3+ substitutions. XRD, FTIR, UV–vis spectroscopy, VSM, SEM and LCR meter are used for the characterizations of the synthesized materials. The optical properties, magnetic properties, structural, morphological, and dielectric properties had been systematically investigated. XRD data and cell refinement study confirmed the hexagonal crystal structure of the synthesized materials that belong to space-group of P63/MMC-(No 194). The values of lattice parameters ‘a’ and ‘c’ have been reduced from their original value 5.9145 Åto 5.8446 Åand 23.239 Åto 23.1684 Åcorrespondingly with doping content. The values of ratio c/a are found within 3.9292 to 3.9641 range, which can be regarded as optimal values for M-type hexaferrites structure as mentioned in previous studies. The crystallite size-(D) and volume-(V) decreases with doping concentration. The band gap of the synthesized materials had shown decreasing trend with doping content. The values of dissipation factor, dielectric loss ε'', and dielectric constant ε', are higher at lower frequency but get smaller as frequency increases. The dissipation factor, dielectric loss ε'', and dielectric constant ε', reduced as the concentration of aluminium is increased. From the analysis of M−H loops it has been concluded that saturation magnetization and remnant magnetization is decreasing with aluminium content, while coercivity is increasing. The anisotropy parameter (B) and anisotropy field (Ha) had shown increasing trend with aluminium concentration. FTIR analysis showed the development of barium hexaferrites in two main absorption-bands, the enormous frequency-band and the low frequency-band. The position of these bands were moved towards a lower frequency range with increasing Al substitution level. The reduction in band gap as well as the enhancement in magnetic and dielectric properties of barium M type hexa-ferrites as a result of aluminium doping making them suitable for various applications, including magnetic storage media, magnetic sensors, microwave devices, electromagnetic wave absorbers and permanent magnets etc.