Room Temperature Dielectric Properties of Polycrystalline FeTeSe ( x = 0.0-0.5).

In this work, frequency-dependent dielectric properties of polycrystalline samples with nominal compositions FeTeSe ( x = 0.0-0.5) were investigated. The samples were synthesized via solid-state reaction method with intermittent grinding at ambient pressure. The phase formation, lattice properties and chemical compositions of the samples were analysed. Dielectric constants ( $\varepsilon ^{\prime }$ , $\varepsilon ^{\prime \prime }$ ), dielectric loss (tan δ) and alternating current (AC) conductivity ( σ ) as a function of frequency ranging from 100 Hz to 10 MHz were measured at room temperature. X-ray diffraction (XRD) data showed the presence of impurity phases of FeO, FeTe and hexagonal FeSe/FeSe. Both a and c lattice parameters decreased with the substitution of Se. Energy-dispersive x-ray spectroscopy confirmed the increasing ratio of Se/Te with x. The measured negative values of real dielectric constant ( $\varepsilon ^{\prime } )$ for x = 0.0-0.5 indicate the conductive nature of these samples. As the Se content was increased, the $\varepsilon ^{\prime } $ became more negative as a result of better grain connectivity as shown by the higher AC conductivity and dielectric loss. [ABSTRACT FROM AUTHOR]