Abstract

Microwave dielectric properties of CaW_1−x(Mo_1/2Te_1/2)_xO₄ (0.01 ≤ x ≤ 0.17) ceramics with (Mo_1/2Te_1/2)⁶⁺ substitution were investigated. For the specimens sintered at 825–950 °C for 3 h, a single phase of a scheelite structure was observed up to x = 0.13, while secondary phases were detected above x = 0.17. The relative densities of the specimens were higher than 95%, and the grain morphologies were uniform and clean for the entire range of compositions. The quality factor (Qf) depended on the intrinsic factors such as the W-site bond characteristics of CaWO₄ evaluated by the bond valence and degree of covalency, and confirmed by the full width at half maximum of the internal mode peak of Raman spectroscopy. However, Qf was also affected by the extrinsic factors, such as the formation of the secondary phases, which showed the maximum Qf value (167,800 GHz) at x = 0.13 and then decreased. The dielectric constant (K) increased with (Mo_1/2Te_1/2)⁶⁺ substitution, which was affected by the dielectric polarizabilities of constituent ions. As the (Mo_1/2Te_1/2)⁶⁺ content increased, the temperature coefficient of resonant frequency (TCF) decreased, which was associated with an increase of oxygen bond valence.

Graphic Abstract

中文翻译：

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取代（Mo 1/2 Te 1/2）6+的CaW 1-x（Mo 1/2 Te 1/2）x O 4（0.01≤x≤0.17）陶瓷的结构特征和微波介电性能

摘要

CAW的微波电介质特性_1-X （沫_1/2特_1/2）_X ø ₄（0.01≤  X  ≤0.17）与（沫陶瓷_1/2碲_1/2）⁶⁺取代进行了研究。对于在825–950°C烧结3 h的样品，观察到白钨矿结构的单相高达x  = 0.13，而在x  = 0.17以上检测到第二相。样品的相对密度高于95％，并且在整个组成范围内，晶粒形态均一且清洁。品质因数（Qf）取决于内在因素，例如通过键价和共价度评估的CaWO ₄的W位键特征，并通过拉曼光谱的内模峰的半峰全宽确定。但是，Qf还受到外部因素的影响，例如次级相的形成，这些次级相在x  = 0.13时显示出最大Qf值（167,800 GHz），然后下降。介电常数（K）随着（Mo _1/2 Te _1/2）^6+的取代而增加，这受到组成离子的介电极化率的影响。作为（Mo _1/2 Te _1/2）⁶⁺含量增加，共振频率温度系数（TCF）降低，这与氧键价的增加有关。

图形摘要