Structural, dielectric and magnetic properties of Sb/Cr-doped CaCu3Ti4O12quadruple perovskite oxides.

Driven by the miniaturization of microelectronic devices and their multifunctionalities, the development of new quadruple-perovskite oxides with high dielectric constants and high Curie temperature are highly required. Herein, we report on the structural, dielectric and magnetic properties of Sb/Cr-doped CaCu₃Ti₄O₁₂(CCTO) quadruple perovskite oxides, CaCu₃Ti_3.9Sb_0.1O₁₂(CCTSO) and CaCu₃Ti₃CrO₁₂(CCTCO). Structural Rietveld refinements demonstrated that the CCTO, CCTSO, and CCTCO ceramics adopted a cubic crystal structure (Im3¯ space group). They exhibited spherical shapes with nearly uniform particle sizes. XPS spectra clarified Cu³⁺ions in the CCTSO ceramics, while Cu²⁺and Cu⁺ions, and Cr³⁺ions in the CCTCO ceramics. All the ceramic samples displayed nearly frequency independent dielectric behaviors at low temperatures but a relaxor dielectric behavior at high temperatures. Such relaxor dielectric behavior in the CCTO and CCTSO ceramics was ascribed to the movement of doubly ionized oxygen vacancies but in the CCTCO ceramics to the movement of singly ionized oxygen vacancies. Impedance and modulus spectra reveal the significance contributions of grains and grain boundaries with non-Debye behavior. At room temperature (RT) the dielectric constant (ϵ_r) and dielectric loss (tanδ) of CCTO ceramics at 1 kHz were 15 922 and 0.126, respectively. An order reduction of tanδwas achieved in the CCTSO ceramics. In the CCTCO ceramics, theϵ_rand tanδat RT and 1 kHz were 975 and 0.453, respectively. The CCTCO powders exhibited antiferroelectric behavior at 2 K with a saturation magnetization (M_S) of 1.42μ_B/f.u., while theM_Sfor the CCTSO powders was only 0.027μ_B/f.u. All ceramic samples exhibited semiconductor characteristics owing to their continuous decreases of resistivity from 2 K to 800 K. Our present work demonstrates an effective route to tuning the dielectric and magnetic properties of CCTO oxides via B-site non-magnetic/magnetic ion-doping.