Development of (Zr,Mn) doped X-type hexaferrites for high frequency EMI shielding applications

Abstract

X-type hexaferrites with nominal composition of [Ba2(Zr0.5Mn0.5)xFe28−xO44+0.25x] where x = 0, 1.5, 2 and 2.5 were synthesized using solid state reaction technique by applying two different sintering conditions of 1240 °C and 1300 °C for 5 h. Phase pure single phase formation of the synthesized hexaferrites were observed using XRD analysis. Surface morphologies of the sintered polished samples were analysed using SEM and found non spherical grains. The average grain size found to be ∼472.9 nm and ∼858.11 nm for the samples sintered using the recipe of 1240 °C and 1300 °C for 5 h respectively. Moreover, the grain size increases with the increase of (Zr,Mn) dopant concentration for the samples sintered at 1240 °C for 5 h and was found decreasing with the increase of (Zr,Mn) dopant concentration for the samples prepared at 1300 °C for 5 h. The average crystallite size estimated using Scherrer’s formula was in the range of 2.4499 nm and 2.275 nm for the samples sintered at 1240 °C and 1300 °C respectively for 5 h. Magnetic measurements (M-H) and (M-T) were performed using vibrating sample magnetometer (VSM). Highest remnant magnetization was found for the material (x = 2) irrespective of the sintering conditions. Saturation magnetisation was found decreasing with increasing of temperature in all the studied samples irrespective of the sintering conditions. Coercivity (Hc) of all the samples found decreasing with the increase in (Mn,Zr) dopant concentration. Electromagnetic interference (EMI) absorption was determined using E5063A Network Analyser (ENA) with the frequency range of (300 MHz-18 GHz). The sample Ba2(Zr0.5Mn0.5)2Fe26O44.5 (x = 2) sintered at 1240 °C, displayed maximum absorption of −36.2 dB (99.975%) at 15.4 GHz with the bandwidth that indicate frequency range in which RL was more than −20 dB (99% absorption) of 0.7 GHz (15.1 GHz–15.8 GHz). The rest of the studied samples displayed the bandwidth of 1.2 GHz (14.4 GHz–15.6 GHz) for minimum 99% absorption. The sample Ba2(Zr0.5Mn0.5)2Fe26O44.5 (x = 2) sintered at 1300 °C, displayed maximum absorption of −35.2 dB (99.97%) at 16.8 GHz with the bandwidth that indicated RL was more than −20 dB (99% absorption) of 1.6 GHz (16 GHz–17.6 GHz). Zr,Mn doped X-type hexaferrites showed better absorption properties in high frequency range (Ku band (12–18) GHz) and as a result, it can be used for EMI shielding for high frequency applications.