熱電材料能透過溫差，將熱能及電能互相轉換，此種特性隨著人類對能源需求的增加及環保意識的興起，而逐漸受到科學家們的矚目。其中，陶瓷熱電材料的鈦酸鍶因其具備良好的高溫化學穩定性、製程較簡單且對環境友善無汙染等優點，使其成為近年來備受期待的熱電材料。
鍶鈦劑量比的調控及稀土元素的摻雜皆為提升鈦酸鍶熱電性質的方式。根據前人的研究，選用與鍶離子半徑較接近的稀土元素，能有效提升鈦酸鍶熱電材料的功率因子。此外，適度的調整鍶鈦之比例，使塊材內部產生鍶空缺，亦會對於電傳導率及熱傳導率有所影響。
本研究以摻釹的鍶不足鈦酸鍶塊材為研究對象，以固相反應法合成摻釹鈦酸鍶Sr0.95-xNdxTiO3 (x = 00, 05, 10, 15, 20, 25)粉體。經成形後，於1450 ℃之氫氬還原氣氛(5 % H2-95 % Ar)中燒結6小時形成塊材，實驗是探討釹含量對鍶不足鈦酸鍶塊材之結晶相、微觀結構及熱電性質的影響。
於結晶相及微觀結構方面，諸塊材試樣均為鈦酸鍶單一相，無第二相的存在，隨著釹含量的增加，晶粒有明顯的成長，其相對密度皆超過 96 %以上。
電傳導率方面，隨著釹含量的增加，塊材的電傳導率亦有明顯的增加，於摻雜25 mol% Nd的試樣達到最大值；諸試樣於操作溫度區間內皆為半導體型轉金屬型的電傳導行為。Seebeck係數方面，諸試樣的Seebeck係數絕對值皆隨著量測溫度的升高而增加，並且呈現N型半導體之特性。摻雜10 mol% Nd及5 mol%鍶不足的塊材試樣於673 K時，具有最佳之功率因子為1400 μW/mK2。
熱傳導率方面，隨著釹摻雜量的提高，塊材的晶格扭曲程度愈大，導致晶格熱傳導率大幅減低。這是因Nd3+離子與Sr2+離子的半徑及重量之差異會影響鈦酸鍶的晶格扭曲所致。摻雜25 mol% Nd之試樣於673 K量測到最低的熱傳導率，為4.11 W/mK。
綜合上述之各項熱電性質，經由公式ZT =(S^2 σ)/κ T計算出各試樣之ZT值，其結果顯示釹元素的摻雜及鍶不足確實能提升鈦酸鍶的熱電性質。摻雜10 mol% Nd及5 mol%鍶不足的試樣具有最佳之ZT值，於673 K為0.19，此值相較於未摻雜Nd之試樣，ZT值提升約90 %。

In this study, crystal structure, microstructure, and thermoelectric properties were assessed to identify the impact of Nd content on Sr-deficiency strontium titanate. Sr0.95-xNdxTiO3 (x = 0.00, 0.05, 0.10, 0.15, 0,20, 0.25) powders were synthesized by solid state reaction and calcined at 1100 ℃ for 5 hours. The mixture powders were formed and sintered at 1450 ℃ for 6 hours under 5 % H2-95 % Ar reducing atmosphere. The crystal structure and microstructure were confirmed by XRD and SEM, respectively. The results showed that the crystal structure of all bulks was mainly SrTiO3 phase. All bulks exhibited dense microstructure with few pores and the average grain size increased monotonically with the increasing content of Nd. The thermoelectric properties were measured from 303 to 673 K.
With the increasing content of Nd, electrical conductivity was enhanced and meanwhile thermal conductivity was reduced. The maximum value of power factor was 1400 μW/mK2 at 673 K for Sr0.85Nd0.1TiO3 bulk. Simultaneously, Sr0.85Nd0.1TiO3 bulk also have the maximum ZT value which was 0.19 at 673 K. This study showed that significant improvements in the thermoelectric power factor could be achieved by the control of the Nd content and Sr-deficiency.

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