Synthesis, structural, electrical and magnetic characterization of apatite-type lanthanide silicates

This article presents an in-depth study on the structural, morphological, electrical and magnetic characterizations of two new phases of apatite-type lanthanide silicates. Polycrystalline samples of neodymium and samarium–manganese silicates (Nd4MnSi3O13 and Sm4MnSi3O13) were synthesized using a high-temperature solid-state reaction route. Rietveld profile refinement of X-ray diffraction data and FTIR analysis revealed that Nd4MnSi3O13 and Sm4MnSi3O13 crystallize in the single-phase apatite-type hexagonal structure with P63/m space group. Scanning electron micrographs showed good crystallinity in the two silicate samples, and the average size of the grains is found to be in submicrons. Frequency dependence of dielectric constant and tanδ for Nd4MnSi3O13 and Sm4MnSi3O13 showed systematic decrement with frequency. DC conductivity studies are indicative of low activation energy and semiconducting nature of Nd4MnSi3O13 and Sm4MnSi3O13. At room temperature, both the silicates exhibit dominant paramagnetism; however, short-range one-dimensional ferromagnetic chains coexist in the paramagnetic state of Nd4MnSi3O13 and Sm4MnSi3O13.