Low temperature sintering and microwave dielectric properties of (Mg3 − xZnx)(VO4)2 ceramics
Low temperature sintering and microwave dielectric properties of (Mg3 − xZnx)(VO4)2 ceramics
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DOI：
10.1016/j.jeurceramsoc.2005.09.099
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发表时间：
2006
影响因子：
5.7
通讯作者：
R. Umemura;H. Ogawa;A. Kan
中科院分区：
文献类型：
--
作者：
R. Umemura;H. Ogawa;A. Kan
本文研究了锌替代镁对(Mg_3-−_xZn_x)(VO_4)_2陶瓷微波介电性能的影响。在烧成温度为750℃时，(Mg_3-−_xZn_x)(VO_4)_2陶瓷的X射线衍射谱在整个成分范围内没有观察到第二相。然而，在850℃烧结的样品中，XRPD分析表明，样品中含有锌钒氧化合物和锌钒氧化合物，这一结果归因于锌钒氧化物相的分解。晶体结构分析表明，Mo6八面体中的M(1)O(M=镁、锌)和M(2)O原子间距增大，而VO四面体中的VO原子间距减小。此外，通过锌取代还观察到M(2)O_6八面体的轻微倾斜。至于阳离子-氧键的共价性，M(1)O_6和M(2)O_6八面体中的MO键的共价性随着Mo原子间距的增加而降低，而VO的共价性则随着锌加入量的增加而增加。然而，由于在这种晶体结构中，MO键的共价性的变化占主导地位，所以阳离子-氧键的共价性略有下降。样品的介电常数在4.4~11.1之间。共价性的降低可能与每种组合物的介电常数的差异有关。(Mg_3-−_xZn_x)(VO_4)_2陶瓷的最大体积密度Q·f值受化学成分的影响，在800-1050°C温度范围内随x的增加而向较低的烧结温度方向移动。样品的共振频率温度系数(τ_f)随Zn含量的增加而减小，τ_f值的变化归因于Zn取代Mg引起M(2)O_6八面体的倾斜。
This paper describes the effects of Zn substitution for Mg on the microwave dielectric properties of (Mg3−xZnx)(VO4)2ceramics. As for the XRPD patterns of (Mg3−xZnx)(VO4)2ceramics sintered at the sintering temperature of 750°C, no secondary phase was detected over the whole composition range. However, in the case of the sample sintered at 850°C, the Zn4V2O9and Zn2V2O7compounds were identified by using XRPD; this result was attributed to the decomposition of Zn3(VO4)2phase. From crystal structure analysis, it was found that the atomic distances of M(1)O (M=Mg and Zn) and M(2)O in MO6octahedra increased, though that of VO in VO4tetrahedron decreased. Moreover, the slight tilting of M(2)O6octahedron was observed by the Zn substitution. As for the covalency of cation–oxygen bond, the covalency of MO bond in M(1)O6and M(2)O6octahedra decreased because of the increase in the atomic distance of MO, whereas that of VO increased with increasing the Zn addition. However, as a result, the slight decrease in the covalency of cation–oxygen bond was recognized because the variation in the covalency of MO bond is predominant in this crystal structure. The dielectric constants of the samples range from 4.4 to 11.1. The decrease in the covalency may be related to the difference in the dielectric constant of each composition. The maximum Q·f value of bulk densities is effected by varying the chemical composition of (Mg3−xZnx)(VO4)2ceramics and it shifts toward lower sintering temperature with an increase in x within the temperature region of 800–1050°C. The temperature coefficient of resonant frequency (τf) of the samples decreased with increasing of Zn, and then a variation in τfvalue was attributed to the tilting of M(2)O6octahedron caused by Zn substitution for Mg.