近幾年發現Tb3Fe5O12於小磁場(1-2 kOe)下可以促發出磁介電性質。一般而言，多鐵性材料必須於大磁場(>1 Tesla)下才具有磁電耦合效應。因此，Tb3Fe5O12的發現提高未來應用的可能性。Tb3Fe5O12屬於稀土鐵石榴石，磁性性質已被廣泛地研究探討，但是研究介電性質的文獻非常稀少。本論文除了探討Tb3Fe5O12介電性質外，並且添加Bi取代Tb研究其對介電與磁性的效應。
　　藉由固相反應法來合成Tb3-xBixFe5O12 (x=0.0-1.0)，結果顯示燒結溫度與Bi的添加巨大地影響Tb3Fe5O12的密度與介電性質，然而燒結溫度對磁性沒有明顯的改變。
較高的燒結溫度增加材料密度、介電常數和耗損峰的頻率，但是降低了Cole-Cole方程式中的α參數。在文獻中，Fe2+/Fe3+ 間的躍遷被用來解釋Tb3Fe5O12的介電行為。另一方面，Bi對Tb的取代增加材料密度與躍遷激發能，但是降低了燒結溫度、介電反應與稀釋Tb對於材料磁性的貢獻。Tb3-xBixFe5O12具有兩個介電鬆弛現象，低溫介電行為由Fe2+/Fe3+ 間的躍遷所產生，而中溫介電行為來自於Bi2+/Bi3+間的躍遷。整個研究中，利用Cole-Cole 方程式與Arrhenius定律來分析介電行為。此外，磁性的實驗結果與文獻相符。

Tb3Fe5O12 showed a large magnetodielectric response at a low field (1-2 kOe). Therefore, it is more promising for practical applications than the multiferroics in which the magnetoelectric coupling only occurred under high field (>1 Tesla). As one of the members of the rare-earth iron garnets, the magnetic properties of Tb3Fe5O12 have been studied extensively, but there is little known about its dielectric properties. In this work, Tb3-xBixFe5O12 (x=0.0-1.0) samples were prepared by the solid-state reaction method at 10001390 °C and their dielectric and magnetic properties were studied in detail. The results revealed that sintering temperature and Bi substitution affected dramatically the density and dielectric behaviors of Tb3Fe5O12, while sintering temperature did not change notably the magnetic properties. Higher sintering temperature resulted in an increase in density, dielectric constant and loss-peak frequency, but a decrease in the α parameter of the Cole-Cole equation. The Fe2+/Fe3+ hopping process was proposed for the observed dielectric behaviors. On the other hand, Bi substitution led to an increase in density and hopping activation energy, but a decrease in sintering temperature, dielectric responses, and the contribution of the Tb3+ magnetic sub-lattice. The intermediate temperature dielectric relaxation may result from the Bi2+/Bi3+ hopping process. The dielectric behaviors were analyzed by using the Cole-Cole method and Arrhenius laws. In addition, magnetic properties were consistent with the reports in the literature.

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