Kui Liu,Huaiwu Zhang,Cheng Liu,Jie Li,Liang Shi,Xueying Wang,Yulong Liao,Lichuan Jin,Dainan Zhang
Herein, Zn 1- x Ca x ZrTa 2 O 8 (0 ≤ x ≤ 0.1) ceramics with wolframite structure were prepared via the solid-state reaction method. Zn 0.94 Ca 0.06 ZrTa 2 O 8 exhibited the best dielectric properties with ε r = 23.14, Q × f = 140,915 GHz (@7.79 GHz), and τ f = −26.42 ppm/°C. ε r increases gradually with the Ca 2+ content. The change in ε r is related to the Ca 2+ ion polarizability and the redshift of Raman vibrational modes. Appropriate Ca 2+ substitution makes the dominant Ta-O have higher lattice energy, resulting in a lower dielectric loss. In addition, the reduction of FWHM of Raman characteristic peaks also had a positive effect on reducing the dielectric loss. First-principles calculations illustrate that the trace substitution of Ca 2+ leads to an increase in the electron cloud density of the [Zn/Ca/ZrO 6 ] octahedra, resulting in lower dielectric losses. Suitable Ca 2+ substitution resulted in higher bond energy and smaller [Zn/Ca/ZrO 6 ] octahedral distortion, implying that τ f is closer to 0 ppm/°C.
Hu Qi,Teng Yuancheng,Zhao Xiaofeng,Zhou Fei,Arslanov Temirlan,Dai Bo
Zn 1− x Ni x ZrTa 2 O 8 ( x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) microwave dielectric ceramics were synthesized by traditional solid-state method. The effect of introducing Ni–O bonds to replace part of Zn–O bonds on the ceramic lattice and microwave dielectric properties was systematically studied. An appropriate amount of Ni 2+ substitution improves the microscopic morphology of crystal, including the grain size, number of pores, number of grain boundaries, and the grain uniformity, giving rise to an increase in the compactness of ceramics and, thereby enhancing the microwave dielectric properties. The Raman analysis prove that the introduction of Ni 2+ is beneficial to enhance the vibrational peak intensity of the oxygen octahedron and effectively improve the Q × f value. However, the introduction of excessive Ni 2+ will lead to the decrease of lattice oxygen and the increase of adsorbed oxygen, and the crystal will become relatively active and unstable, and the microwave performance will decrease. In addition, the substitution of Ni 2+ can also effectively control the resonance temperature coefficient, which is beneficial to improve the τ f value. As a result, Zn 0.94 Ni 0.06 ZrTa 2 O 8 exhibits excellent microwave dielectric properties: ε r = 32.15, Q × f = 15,7500 GHz, τ f = − 33.1 ppm/°C, presenting as a potential candidate for low-loss microwave dielectric materials.
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