目前已知有許多正方鎢青銅礦結構(TTB)的鈮酸鹽具有鐵電性質，而本研究將基於此特性，對此類化合物摻雜過渡金屬或稀土元素等磁性粒子，並研究其磁電特性，藉此尋找新複鐵式材料。
　　本研究利用固相繞結法合成K3TMxNb5O15與Ba6TMxNb9O30兩種體系的化合物，並改變其中的TM元素(TM=Fe, Co, Ni, Mn)，期望能夠合成出單一相複鐵式化合物，並使用自發成核法進行單晶成長，以得到高純度樣品作後續性質的分析與量測。
　　實驗結果發現Ba6Mn0.67Nb9.33O30成份具有弛緩型鐵電材料的性質，呈現一寬廣的介電常數峰值且最大介電常數會隨頻率的上升而下降，而Ba6FeNb9O30、Ba6Mn0.67Nb9.33O30和K3Fe1.33Nb4.6O15三種成份化合物的電滯曲線皆有滯迴的現象存在。Ba6FeNb9O30的磁滯曲線在5K下則呈現非線性的軟磁性質，並根據磁化率倒數隨溫度變化圖推測其在110K有一磁轉換溫度，高於110K則轉換為順磁性。而Ba6CoNb9O30成份則可能具有亞鐵磁性質。另外由單晶繞射數據可知TM離子(如Fe等)取代於Nb位置，是以(Fe, Nb)混雜排列的形式存在。

　　Many tetragonal-tungsten-bronze (TTB) structured niobates are known to be ferroelectric. In the present work, they were doped with transition metal (TM) ions and the electrical and magnetic properties of the doped samples were investigated in order to search for new multiferroic materials.
　　Two different kinds of TTB structured niobates, i.e. K3TMxNb5O15 and Ba6TMxNb9O30 (TM=Fe, Co, Ni, Mn) have been prepared by the conventional solid-state method. In addition, single crystals of some samples were also been grown by the spontaneous nucleation technique in an attempt to obtain high-purity samples for electrical and magnetic characterizations, so that the intrinsic properties can be identified.
　　A broad dielectric peak with frequency dispersion was observed for the sintered Ba6Mn0.67Nb9.33O30 ceramics, indicating relaxor behavior. Some samples, such as Ba6FeNb9O30, Ba6Mn0.67Nb9.33O30 and K3Fe1.33Nb4.6O15 ceramics, showed hysteresis loops in the polarization vs. electrical field measurements. However, the loops were unable to reach a saturated state and therefore it is unclear that if they are indeed ferroelectric. Magnetic hysteresis curves were also observed for the Ba6FeNb9O30 single crystal samples in the moment vs. magnetic-field measurement at 5K, but the moment was very small and therefore it was unable to confirm if it is ferromagnetic. The temperature dependence of inverse magnetic susceptibility showed some abnormality at 110 K for the Ba6FeNb9O30 crystals, implying that there was some kind of magnetic phase transition. For the Ba6CoNb9O30 crystals, the temperature-dependent susceptibility measurements showed ferrimagnetic property. On the other hand, structural analysis by x-ray single crystal diffraction revealed that the substitution of TM ions (e.g. Fe et al.) was taken place at the Nb site, which implies the random distribution of (Nb, Fe) at the same crystallographic site.

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