Effect of La-Na Doping in Co-Ti Substituted Barium Hexaferrite on Electrical and X-Band Microwave Absorption Properties AMIT ARORA 1,2 and SUKHLEEN BINDRA NARANG 2,3 1.—D.A.V. Institute of Engineering and Technology, Jalandhar, India. 2.—Department of Electronics Technology, Guru Nanak Dev University, Amritsar, India. 3.—e-mail: sukhleen2@yahoo.com Lanthanum and sodium co-substituted barium hexaferrite Ba (1À2x) La x Na x- Fe 10 CoTiO 19 (x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25) samples were prepared using a conventional solid state reaction route. Structural, morphological, electrical and microwave absorption properties of synthesized hexaferrites were investigated using various instruments including x-ray diffractometer (XRD), scanning electron microscope (SEM), impedance analyzer and vector network analyzer. Single phase formation was confirmed by XRD analysis. Unit cell volume decreased with increase in concentration. Average grain size as estimated from SEM micrographs lies in 0.73–1.15 lm range. The DC re- sistivity decreased with increase in La-Na concentration. The dielectric parameters were measured in the 10 kHz–1 MHz frequency range. At lower frequencies, dielectric constant (e¢) and tangent loss (tan d) values were high, which decreased with increases in frequency. Electromagnetic and microwave absorption properties were evaluated theoretically in the X-band (8.2– 12.4 GHz) for different sample thicknesses. The microwave absorption anal- ysis suggests that the sample with composition Ba 0.80 La 0.10 Na 0.10 Fe 10 CoTiO 19 could be an effective microwave absorbing candidate for microwave applica- tions in the X-band frequency range. Key words: Hexaferrite, XRD, SEM, reflection loss, AC conductivity, complex permittivity, complex permeability INTRODUCTION Hexaferrites are among the materials most explored for their applications in high frequency devices. Barium hexaferrite, with chemical formula BaFe 12 O 19 and magnetoplumbite structure, has been broadly explored due to its fascinating proper- ties, such as corrosion resistance, high saturation magnetization, high coercivity, and low-cost synthe- sis. 1–3 M-type BaFe 12 O 19 hexagonal ferrite (BAHF) in unaltered and altered or doped form is appropri- ate for applications in magnetic recording media, communication devices, anechoic chambers, electro- magnetic interference (EMI) reduction, as hard magnets, and in radar absorbing materials (RAMs) utilized as a part of stealth technology. 4,5 Barium hexaferrite has been synthesized by different inves- tigators using conventional reaction method utiliz- ing oxides or carbonates of the required materials by two-phase sintering at 1200–1300°C. 6,7 In liter- ature, reports are available for the preparation and characterization of BAHF doped with various ions such as La, Pr, Co, Gd, Al, Mn, Zr, Mg. 3,6,8,9 These investigations show that the structural, electrical, dielectric and microwave absorbing characteristics of BAHF are highly affected by the doping of multivalent cations. In our study, Lanthanum is chosen because of its higher solubility in Barium/ Strontium hexaferrites in comparison to other lan- thanides, and because it has a remarkable influence on the magnetic and dielectric properties of the hexagonal ferrites. 4,10 Sodium is chosen to balance the valency, i.e., it maintains electro-neutrality of (Received August 31, 2017; accepted April 27, 2018) Journal of ELECTRONIC MATERIALS https://doi.org/10.1007/s11664-018-6349-8 Ó 2018 The Minerals, Metals & Materials Society