Microstructural characterisation and microwave absorption characteristics of La_(1-x)Ba_xFe_0.25Mn_0.5Ti_0.25O₃ (x = 0, 0.25, 0.75, 1)

Perovskite lanthanum manganites, especially those doped LaMnO₃ (LMO), have shown potentials for applications in magnetic electronic functional materials. Partial substitution of La ion with divalent ions or Mn ion with trivalent ions gives rise to new properties. Substituted LMO has ability for absorbing electromagnetic waves. In this paper, we report recent investigations on substituted LaMnO₃ with designated La_(1-x)Ba_xFe_0.25Mn_0.5Ti_0.25O₃ (x= 0, 0.25, 0.75, 1) compositions. Materials were prepared by mechanical alloying technique. After heat treatments at sintering temperatures 1100°C, 1200°C and 1300°C to the quasi-crystalline powders, presence of material phases were confirmed by XRD. Single phase material was obtained in samples of 0.25 ≤ x < 0.75 compositions. Mean crystallite size of sintered materials showed that crystallites were in a Nano crystalline regime. It is then concluded, during mechanically alloyed sintering powder materials, solid-state reaction and crystallisation promoted formation of particles containing Nano crystallites. Microwave absorption data showed that materials with large amount of substituted Ba ion gives broad absorption profiles. Total substitution of La by Ba ions (x=1) has significantly changed absorption profile. Smaller mean crystallite sizes indicated an increase in reflection loss value. In this report, empirical relationship between nanostructure and absorption profile of material is discussed.