Herein, Mg 1− x Ni x ZrTa 2 O 8 ( x = 0, 0.1, 0.3, 0.5, 0.8, 1) ceramics are synthesized using a solid-phase reaction method. Ni 2+ replacing Mg 2+ improves the drawback of high sintering temperature and poor temperature stability. The samples have a relative density above 95% at the optimal sintering temperature. The sintering temperature of Mg 1− x Ni x ZrTa 2 O 8 reduces from 1475 to 1400 °C. And single-phase Mg 1− x Ni x ZrTa 2 O 8 ceramics with monoclinic wolframite structures are analyzed. According to the Rietveld refinement results, with the doping of Ni 2+ , the transformation of unit cell volume leads to the shift of the main peak in the X-Ray diffraction pattern to a higher angle in 0 ≤ x ≤ 0.3 and a lower angle in 0.5 ≤ x ≤ 1. The ε r of Mg 1− x Ni x ZrTa 2 O 8 is comparable to MgZrTa 2 O 8 . At 1400 °C, the Q × f is increased from 10 598 GHz in the undoped sample to 43 041 GHz in Mg 0.9 Ni 0.1 ZrTa 2 O 8 ceramic. The absolute values of τ f of ceramic samples decrease with the excessive Ni 2+ . The desirable dielectric properties ( ε r = 20.79, Q × f = 43 041 GHz, τ f = −33.04 ppm °C −1 ) are obtained at 1400 °C. Ni substitution is effective for MgZrTa 2 O 8 ceramic to optimize densification temperature and retain the high Q × f value.
Compared to Te, Ni is found in abundance in the earth's crust. At the same time, the mechanical properties of Ni atom-substituted skutterudite are significantly improved. In this study, a series of S-filled Ni-substituted skutterudite compounds were synthesized by a high-pressure and high-temperature (HPHT) method in the synthesis pressure range of 1.0–3.0 GPa. The phase composition, microscopic morphology, and electrothermal transmission properties of the S x Co 3.6 Ni 0.4 Sb 12 ( x = 0, 0.05, 0.10, 0.20) samples were systematically characterized. Phase composition analysis showed that the introduction of S atoms into the intrinsic pores of skutterudite can improve the solid solution limit of Ni atoms in the Co sites of skutterudite. The filling limit of S increased with the synthetic pressure. Moreover, microscopic morphology analysis revealed that the filling of S atoms inhibited the growth of grains. A large number of lattice fringes in different directions were found in the sample, containing abundant microstructures such as lattice distortions and dislocation defects. Compared with the synthesized samples, S 0.05 Co 3.6 Ni 0.4 Sb 12 synthesized at 1.0 GPa had a maximum room temperature power factor of 7.98 × 10 −4 Wm −1 K −2 . The electrical properties of S 0.05 Co 3.6 Ni 0.4 Sb 12 samples stored for 6 months without any protective measures were tested at room temperature. No obvious changes in performance were observed, which proved that the HPHT method can synthesize stable samples. After several thermal cycles, the electrical properties of the S 0.05 Co 3.6 Ni 0.4 Sb 12 sample was tested for variable temperature, and it was found that the sample still had good stability. How the substitution of S atoms with Ni atoms reduces the lattice thermal conductivity can be explained by fitting the Callaway model. The S 0.05 Co 3.6 Ni 0.4 Sb 12 sample synthesized at 1.0 GPa had a maximum zT value of 0.46 at the test temperature of 773 K, which decreased to 0.43 after multiple thermal cycles at the same temperature.
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.
危险品化学品经营许可证（带存储）