Ba5Nb4O15 材料成份系統由於具有高介電係數 (εr)、高品質因數 (Q) 和趨於零的共振頻率溫度係數 (τf)，而被廣泛應用於微波介電材料的研究上，然而大多數的研究都是在探討外在因素對電性的影響，像是藉由製程提昇密度來增進介電性及第二相 (second phase) 對介電性質的影響等，鮮少有文章在探討成分內在結構因素與電性質方面的相互關係。

　　過去的研究指出，添加 Sr2+ 於 Ba5Nb4O15 成分中，能夠完全固溶形成 (Ba(1-x)Srx)5Nb4O15 成份系統，而不會產生第二相，故本實驗以結晶化學的方法，探討當不同添加量的 Sr2+ 固溶進入 Ba5Nb4O15 結構時，其晶體結構變化對電性質的影響。

　　結果發現介電常數與晶格常數 c-a ratio 成正比，這是因為在 c-a ratio 有最大值時，晶格比例在 c 軸方向呈現最狹長狀態，使離子極化在 c 軸方向作用更大，極化量增加。另外，推測介電常數與晶格內，A、B-site陽離子偏離周圍氧離子中心的距離及陽離子空間的大小相關。在共振頻率溫度係數部分，發現其與 c-a ratio 及介電係數變化的趨勢一致，但目前影響的機制不明。

　　Ba5Nb4O15 ceramics with high permittivity (εr), high quality factor (Q), and low temperature coefficient of resonators frequency (τf), are investigated on microwave dielectric materials extensively. However, most papers focus on the relationships between microwave properties and extrinsic parameters (second phase, density etc.), few published papers investigates the phenomena between intrinsic parameters and dielectric properties at microwave frequency.

　　In this investigation, we dope Sr2+ into Ba5Nb4O15 to form (Ba(1-x)Srx)5Nb4O15 solid solution system to discuss the relation between crystal structure and microwave dielectric property.

　　Depending on the result, the dielectric constant is in direct proportion to the cell parameter c-a ratio. Otherwise, the dielectric constant is related to the space of the A, B-site cation and the distance of the A, B-site cations diverge from the center of nearby oxygen ions. For the temperature coefficient of resonators frequency, it is in direct proportion to the cell parameter c-a ratio and dielectric constant, but the mechanism is ambiguous.

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