Synthesis and dielectric properties, XPS spectroscopy study of high-entropy pyrochlore

It was established by XRD, that ceramics of the nominal composition Bi2Cr1 / 6Mn1 / 6Fe1 / 6Co1 / 6Ni1 / 6Cu1 / 6Ta2O9+Δ, regardless of the synthesis conditions, contained trace amounts of bismuth orthotantalate impurity. The phase-clean sample was obtained with a deficiency of bismuth atoms in the Bi2−хCr1 / 6Mn1 / 6Fe1 / 6Co1 / 6Ni1 / 6Cu1 / 6Ta2O9+Δ bismuth sublattice. The complex oxide crystallizes in the pyrochlore structural type (sp. gr. Fd-3m, а =10.4811(2) Å). Ceramics is characterized by a porous, loose microstructure with an average grain size of 0.5 –1 μm. According to the XPS data, the transition element ions in pyrochlore are predominantly in the Cr (III), Fe (III), Mn (II), Co (II), Ni (II), Cu (II) states. At room temperature, the permittivity and dielectric loss tangent of Bi2−1 / 3Cr1 / 6Mn1 / 6Fe1 / 6Co1 / 6Ni1 / 6Cu1 / 6Ta2O9+Δ are ≈46 and ≈0.004 at 1 MHz, respectively. An equivalent circuit is proposed that simulates the electrical properties of the sample.