Effects of Y₂O₃/CeO₂ co-doping on microwave dielectric properties of Ba(Co_0.6Zn₃₈)_1/3Nb_2/3O₃ ceramics

The effects of CeO₂/Y₂O₃ co-doping on the microstructure and microwave dielectric properties of Ba(Co_0.6Zn_0.38)_1/3Nb_2/3O₃-xA-xB (x = 0,1,2,3,4,6; A = 0.1204 wt%Y₂O₃; B = 0.1 wt%CeO₂) ceramics prepared by the conventional solid-state route technique were investigated. The X-ray diffraction (XRD) results presented that all the well sintered samples exhibited the main phase BaZn_0.33Nb_0.67O₃−Ba₃CoNb₂O₉. A certain amount of Ba₈CoNb₆O₂₄ surface secondary phase and minority phase of Ba₅Nb₄O₁₅ were also observed in all sintered ceramics. The 1:2 B-site cation ordering degree was found to influenced by the substitution of Y³⁺ and Ce⁴⁺ in the crystal lattice, especially for x = 0.02. Then the scanning electron microscopy (SEM) picture of the optimally well-sintered (1350 °C for 20 h) ceramic has shown a dense microstructure. Although the ε_r almost kept unchanged, appropriate doping content would greatly improve the Q × f value. Meanwhile, the τ_f value first declined and then increased with increasing x. At last, the excellent microwave dielectric properties of ε_r = 36.09, Q × f = 72006 GHz, τ_f = 3.35 ppm/ºC were obtained for the ceramic with x = 0.02 sintered in air at 1350 °C for 20 h. - Graphical abstract: Fig. SEM images of as-sintered Ba(Co_0.6Zn_0.38)_1/3Nb_2/3O₃-xA-Xb (A = 0.1204 wt%Y₂O₃; B = 0.1 wt%CeO₂₎ceramics: (a) x = 0,(b) x = 0.01,(c) x = 0.02,(d) x = 0.03, (e) x = 0.04,(f) x = 0.06. The images confirmed the presences of two phases on the surface of the ceramics, plate-shaped grains (Ba₈(C_O,Zn)₁Nb₆O₂₄phase) and needle-shaped grains (Ba₃(Co_0.6Zn_0.38)₁Nb₂O₉ phase). As a small content of CeO₂/Y₂O₃ (x = 0.01–0.04) was codoped into the BCZN ceramics, the amount of Ba₈(C_O,Zn)₁Nb₆O₂₄ phase was found to decrease significantly. - Highlights: • The amount of secondary phase decreased with CeO₂/Y₂O₃ co-doped into BCZN ceramics. • The ordering degree was increased by substitution of Y³⁺/Ce⁴⁺ in crystal lattice. • Appropriate doping content of CeO₂/Y₂O₃ have greatly improved the Q × f value. • A ceramic material with excellent dielectric properties was synthesized.