Influence of Ce Substitution for Bi in BiVO₄ and the Impact on the Phase Evolution and Microwave Dielectric Properties

Abstract

In the present work, the (Bi1-xCex)VO4 (x ≤ 0.6) ceramics were prepared via a solid-state reaction method and all the ceramic samples could be densified below 900 °C. From the X-ray diffraction analysis, it is found that a monoclinic scheelite solid solution can be formed in the range x ≤ 0.10. In the range 0.20 ≤ x ≤ 0.60, a composite region with both monoclinic scheelite and tetragonal zircon solid solutions was formed and the content of the zircon phase increased with the calcined or sintering temperature. The refined lattice parameters of (Bi0.9Ce0.1)VO4 are a = 5.1801(0) Å, b = 5.0992(1) Å, c = 11.6997(8) Å, and γ = 90.346(0)° with the space group I112/b(15). The VO4 tetrahedron contracts with the substitution of Ce for Bi at the A site, and this helps to keep the specific tetrahedron chain stable in the monoclinic structure. The microwave dielectric permittivity was found to decrease linearly from 68 to about 26.6; meanwhile, the quality factor (Qf) value increased from 8000 GHz to around 23900 GHz as the x value increased from 0 to 0.60. The best microwave dielectric properties were obtained in a (Bi0.75Ce0.25)VO4 ceramic with a permittivity of ∼47.9, a Qf value of ∼18000 GHz, and a near-zero temperature coefficient of ∼+15 ppm/°C at a resonant frequency of around 7.6 GHz at room temperature. Infrared spectral analysis supported that the dielectric contribution for this system at microwave region could be attributed to the absorptions of structural phonon oscillations. This work presents a novel method to modify the temperature coefficient of BiVO4-type materials. This system of microwave dielectric ceramic might be an interesting candidate for microwave dielectric resonator and low-temperature cofired ceramic technology applications.

Vibrational spectroscopic and crystal chemical analyses of double perovskite Y2MgTiO6 microwave dielectric ceramics

“…There are no studies analyzing the structure‐property relationship via vibrational spectroscopy or the chemical bond characteristics of Y 2 MgTiO 6 for MWDCs applications. In this regard, Zhou et al verified that Raman spectroscopy was a crucial technique to identify phase composition and phase evolution . Relevant Ruddlesden‐Popper structures and trirutile‐type Co 0.5 Ti 0.5 TaO 4 were designed, and crystalline information and intrinsic microwave dielectric characteristics were investigated through vibrational mode analysis.…”

High‐Q microwave ceramics of Li2TiO3 co‐doped with magnesium and niobium

“…With the development of wireless communication, the search for low‐cost microwave dielectrics with high Q factor becomes one of the most popular researches in the field of dielectrics because of their potential applications in microwave substrates, resonators, filters and patch antennas . The material with high Q factor can provide better frequency control accuracy and higher passband edge signal frequency response steepness.…”

Synthesis of Zn0.5Ti0.5NbO4 microwave dielectric ceramics with Li2O‐B2O3‐SiO2 glass for LTCC application

“…Fabrication of ceramics usually requires high sintering temperature (>1000°C), such as the commercial microwave dielectric materials of BaO‐TiO 2 (densification of BaTi 4 O 9 demands a high temperature of 1300°C), Ba(Zn 1/3 B 2/3 )O 3 (sintering temperature of 1500°C‐1650°C for B = Nb, 1500°C for B = Ta), and their suitable temperatures exceed 1300°C, which is very energy‐consuming. For the sake of conserving energy, low‐temperature co‐fired ceramic (LTCC) technology emerges as the time requires, besides, LTCC plays an important role in passive integration, reducing circuit dimension, which can improve the flexibility of the design of circuits, however, LTCC application demands a low sintering temperature for the co‐firing with Ag and Cu electrodes (melting point of Ag, Cu is 961°C and 1083°C, respectively), the materials should also maintain great microwave dielectric properties, such as Bi 2 O 3 ‐TiO 2 ‐V 2 O 5 , Bi‐Li‐Ta, and BiVO 4 ‐LaNbO 4 system studied by Zhou, the sintering temperature of ceramic can be decreased to 800°C and still maintain great properties …”