Dielectric and magnetic properties of Nb substituted hexagonal Ba₆Y₂Ti₄O₁₇ (BYTO) perovskite oxides

In this study, niobium (Nb) substituted barium yttrium titanates, Ba₆Y₂Ti_4−xNb_xO₁₇, (BYTNbO, x = 0.0, 0.05, 0.1, and 0.2), were synthesized via semi-wet route at a relatively low sintering temperature. Rietveld refinement of the X-ray diffraction patterns of BYTNbO confirmed that all the compositions have a hexagonal layered perovskite structure with the space group of P6₃/mmc. Nb⁵⁺ substitution at Ti-site in Ba₆Y₂Ti₄O₁₇ (BYTO) induces the formation of magnetically active ion of Ti³⁺ to enhance the magnetization. Remnant magnetization and magnetic coercivity were increased with decreasing temperature due to the disordered magnetic domains. The magnetization of Ba₆Y₂Ti_3.9Nb_0.1O₁₇ also increased to 3.68 × 10⁻⁴ emu g⁻¹ by Nb substitution in BYTO. The Curie temperature of x = 0.05, 0.1, and 0.2 were found to be 15.76, 17.77, and 14.12 K, respectively. The dielectric properties of all the compositions were investigated in the frequency range of 100–5.5 MHz. The dielectric constant (ε_r) was varied from 1.1 × 10³ to 2.18 × 10³ with the amount of Nb substitution in BYTO. An impedance spectroscopic study revealed the presence of semiconducting grain and an insulating grain boundary, both of which supports the internal barrier layer mechanism and are responsible for the high dielectric constant in these materials.