熱電材料為一種能將熱能與電能相互轉換的功能性材料，能夠將廢熱回收再利用，對於節能減碳與能源回收方面有很大的幫助。鈦酸鍶在高溫下具有高溫化學穩定性與低毒性的優勢。相較於其他氧化物熱電材料，鈦酸鍶擁有較高的Seebeck係數，易於透過摻雜來提升載子濃度，進而提升電傳導率。因此異價摻雜的鈦酸鍶塊材為一種具有發展前途的N型熱電材料。
相較於單一摻雜鈦酸鍶，共摻雜的鈦酸鍶能同時擁有摻雜兩種不同元素的性質，因此能同時維持好的導電性並減少其熱傳導性。而兩種元素在鈦酸鍶中的固溶極限也會影響材料內部的微觀結構與熱電性質。
本研究檢討釹、鏑共摻雜鈦酸鍶之熱電性質，實驗是固定釹之摻雜量而改變鏑之摻雜量，以固相合成法製備Nd0.1Sr0.9-xDyxTiO3 (x = 0, 0.01, 0.03, 0.05, 0.07, 0.09) 粉末，經冷均壓成形後，於1500 ℃還原氣氛中燒結6小時形成塊材，塊材之結晶相及顯微結構是以XRD及SEM分析，而熱電性質之量測範圍為303~673 K。
結果顯示合成粉體除鈦酸鍶主相外，Dy0.07與Dy0.09試樣亦含有少量第二相Dy2Ti2O7。粉體經燒結成塊材後僅Dy0.09試樣含有第二相Dy2Ti2O7，燒結塊材之相對密度介於92~96 %。
各塊材之電傳導率皆是隨溫度之增加呈現先增後減的趨勢，其電傳導行為是由半導體型轉成金屬型。而隨Dy含量越多，電傳導率有提升之趨勢，但過多第二相Dy2Ti2O7也會使電傳導率些微降低。隨Dy含量越多，塊材的Seebeck係數絕對值有減少之趨勢，所有試樣均為N型半導體之特性。綜合上述電傳導率與Seebeck係數後，經過計算，Dy0.07試樣於623 K時，具有最高之功率因子為1100 μW/mK2。
熱傳導率方面，隨Dy的摻雜量增加，熱傳導率隨之減少。Dy造成鈦酸鍶的晶格扭曲程度越大，越能降低晶格熱傳導率。另外第二相Dy2Ti2O7亦會造成熱傳導率的減少，在所有塊材試樣中，Dy0.09試樣於673 K所量測到的熱傳導率最低，為3.91 W/mK。
綜合各項熱電性質後計算試樣之ZT值，結果顯示Nd及Dy共摻雜能夠有效提升鈦酸鍶的熱電性質，Dy0.07試樣具有最佳之ZT值，於673 K為0.18，此值相較於單一摻雜Nd的Dy0.00試樣，ZT值提升了約80 %。

Doped SrTiO3 materials have been a promising n-type thermoelectric material. Compared with single-doped SrTiO3, co-doped SrTiO3 could simultaneously possess two different properties, thereby maintaining good electrical conductivity and reducing thermal conductivity. To improve the thermoelectric properties of SrTiO3, Nd and Dy were doped in SrTiO3 in this study. Nd0.1Sr0.9-xDyxTiO3 (x=0~0.09) powders were prepared via a traditional solid state reaction. The powders were formed and sintered at 1500 ℃ for 6 hours under a reducing atmosphere of 5 vol % hydrogen in argon. The crystal structures and microstructures were observed by XRD and SEM. Thermoelectric properties were measured from 303 to 673 K. The crystal structure of powders was mainly cubic SrTiO3. and there was the minor phases Dy2Ti2O7 observed in the Dy0.09 bulk sample because the doping amount of Dy exceeds solid solution limit of SrTiO3. The relative density of the sintered bulk is between 92% and 96%.With the increasing amounts of Dy, electrical conductivity was enhanced and Seebeck coefficient decreased. However, the minor phase Dy2Ti2O7 lead to the decrease of electrical conductivity for Dy0.09 sample. All samples were characterized by n-type semiconductor-like behavior. The maximum value of power factor was 1100 μW/mK2 at 623K for Dy0.07 sample. In terms of thermal conductivity, as the doping amount of Dy increases, the thermal conductivity decreases, and the lattice distortion of SrTiO3 increases, which can effectively reduce the lattice thermal conductivity. In addition, the second phase Dy2Ti2O7 also caused a decrease in thermal conductivity. Among all the bulk samples, the Dy0.09 sample had the lowest thermal conductivity measured at 673 K, which was 3.91 W/mK.The results show that the co-doping of Nd and Dy can effectively improve the thermoelectric properties of SrTiO3. The Dy0.07 sample has the best ZT value, which is 0.18 at 673 K. This value increases about 80% compared to the single doped Dy0.00 sample.

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