Dielectric Relaxation and Magnetic Structure of A-Site-Ordered Perovskite Oxide Semiconductor CaCu₃Fe₂Ta₂O₁₂

Abstract

A new perovskite oxide semiconductor, CaCu3Fe2Ta2O12, was synthesized through a high-pressure and high-temperature approach. The compound possesses an Im3̅ space group, where it crystallizes to an A-site-ordered but B-site partial ordered quadruple perovskite structure. Spin ordering occurs around 150 K owing to the antiferromagnetic coupling between Fe3+ spins and ferromagnetic coupling between Cu2+ spins. The room-temperature dielectric permittivity of CaCu3Fe2Ta2O12 was measured to be approximately 2500 at 1 kHz. More importantly, isothermal frequency-dielectric spectroscopy demonstrates the existence of two dielectric relaxations. Debye-like relaxation is attributed to charge carriers trapped among the oxygen vacancies at low temperatures and Maxwell–Wagner polarization relaxation at high temperatures. CaCu3Fe2Ta2O12 is a new magnetic semiconductor, where A-site ordering is intercorrelated with second-order Jahn–Teller distortion. These findings offer opportunities to design novel perovskite oxides with attractive magnetic and dielectric properties.

Research progress on quadruple perovskite oxides

“…At a greater temperature, the thermally stimulated procedure of the charge carriers causes the ε r to increase stepwise. 105 Furthermore, as illustrated in Fig. 24(b), two frequency dependence of tan δ between 100 and 300 K can be clearly seen, corresponding to two dielectric relaxations designated as A and B.…”

“…49(b) are 0.37 and 0.27 nm, respectively, which are consistent with the improved lattice parameters. 105 The SAED patterns and TEM images of LCFTSO are displayed in Fig. 50(a)-(c).…”

“…49(b) are 0.37 and 0.27 nm, respectively, which are consistent with the improved lattice parameters. 105…”

Magnetism in Cation-Ordered Multicomponent Oxide Perovskites

“…So far, two categories of such A-site- and B-site-ordered multicomponent perovskite-derived structures have been reported, namely, double double perovskites and quadruple perovskites. There are several examples of double double perovskites with 1:1 ordering of A/A′ and B/B′ cations like NaLaMgWO 6 , KLaMgTeO 6 , NaLaMgTeO 6 , KLaMgWO 6 , NaLaCoWO 6 , NaLaNiWO 6 , and NaLaScNbO 6 , − as well as quadruple perovskites with 1:3 cation ordering at the A site and 1:1 ordering at the B site like CaCu 3 Fe 2 Ta 2 O 12 , CaCu 3 Cr 2 Sb 2 O 12 , and CaCu 3 Fe 2 Sb 2 O 12 . − While the A site in the basic ABO 3 perovskites is usually occupied by alkali-metal, alkaline-earth, or rare-earth cations, the derived structures as in the quadruple perovskite of the general formula AA′ 3 B 2 B′ 2 O 12 can accommodate transition metal (TM) ions . Employing the high-pressure synthesis route, in recent times, it has also been possible to put small-sized TM ions such as Mn 2+ or Cu 2+ at the A-sites of double double perovskites, along with large, alkaline-metal cations like Ca 2+ or Sr 2+ .…”

Highly Reversible Ambipolar Photocurrents by Modulating Ta in Ba2Bi2–xTaxO6 Double Perovskites

“…The electrochemical instability of Ba 2 Bi 1.8 Ta 0.2 O 6 photoelectrodes is a major issue, while highly reversible ambipolar photocurrents are observed for photoelectrodes with x ≥ 0.4. This intriguing polarizable behavior could be ascribed to the space charge polarization caused by the accumulated charge carriers in the grain boundaries, , or stem from the orientational crystal domain and domain wall effects, which could vastly expand its application, e.g., not only to the protection overlayer and the visible-light responsive hole transporting layer for a homojunction structure with the La 3+ -doped BBO system for solar water splitting, but also to fulfill a demand for photocurrent-switchable optoelectronic devices. , …”