Structural, magnetic, dielectric and electrical transport properties of CaCu3Ti2FeVO12 quadruple perovskite oxides synthesized at ambient pressure

Quadruple perovskite oxides (QPOs) of CaCu₃Ti₂FeVO₁₂ (CCTFVO) were synthesized at ambient pressure, and their structural, dielectric, magnetic and electrical transport properties were investigated. The CCTFVO compounds crystallize in a cubic crystal structure with space group of Im$\overline{3}$ and lattice parameter of a = 7.3903(8) Å. XPS spectra verify the coexistence of Ti³⁺/Ti⁴⁺ and Fe²⁺/Fe³⁺ pairs in this compound. The CCTFVO ceramics displayed pronounced frequency-dependent dielectric behaviour, and a relaxor-like dielectric response appeared between 173 K and 450 K. That was ascribed to the movement of double-ionized oxygen vacancies with thermal activation energy of 1.10 eV. At 100 kHz and 300 K, the CCTFVO ceramics had relative dielectric constant (ε_r) of ∼ 138 and dielectric loss (tanδ) of 0.56. A diffuse phase transition undergoes near 330 K under 1 kHz. The CCTFVO QPOs exhibit ferrimagnetism at 2 K with saturated magnetization of 1.11 μ_B/f.u. and magnetic T_C = 623 K. The Curie-Weiss fitting of the inverse magnetic susceptibility (χ^-1) versus temperature curve, yielded the positive θ_P value of 767 K, confirming the predominant ferromagnetic interactions in the CCTFVO powders. From the Curie constant (C = 0.199 emu⋅K⋅mol^-1), the effective magnetic moment was calculated as μ_eff = 1.22 μ_B/f.u., which was smaller than the theoretical value of 6.60 μ_B/f.u. Below ∼ 166 K the zero-field cooling (ZFC) and field-cooling (FC) curves became bifurcated each other, and the ZFC curve decreased further upon cooling. This phenomenon is attributed to the presence of short-range spin clusters in the ferromagnetic background. It can be ascribed to the partial disorder of B-site ions, leading to local random potentials and consequently resulting in local competition between the ferromagnetic state driven by double-exchange interactions and antiferromagnetic state driven by superexchange interactions. The resistivity (ρ)-temperature (T) data confirm the semiconducting behaviour of the CCTFVO ceramics, which are fitted by Mott’s variable range hopping model, thermally activated semiconductor conductivity model, and small polaron hopping model, respectively.