為提升鈦酸鍶塊材之熱電性質，本研究選用La、Nd二元素共摻雜於鈦酸鍶當中，其試樣表示為Sr0.9La0.1-xNdxTiO3 (x = 0~0.1)，探討不同La、Nd共摻雜量對鈦酸鍶粉末燒結及熱電性質之影響。
固體粉末原料經由球磨混合、兩次煆燒成相、冷均壓成形後，於1500 ℃氬氫(5%H2-95%Ar)還原氣氛中燒結4小時。試樣之結晶相、顯微結構及元素分析是以XRD、SEM、EDS及XPS分析，熱電性質之量測範圍為303 ~ 673 K。
結晶相及微結構方面，不同鑭、釹共摻雜量之鈦酸鍶塊材，其結晶繞射訊號均為單一相鈦酸鍶，各試樣之微結構相似，晶粒相近，約2~3 μm，平均相對密度為86%。
電傳導特性方面，各試樣於量測溫度範圍內均呈現N-type電傳導，隨著La摻雜量比例之增加，塊材之電導率有逐漸增加之趨勢，而適量La、Nd共摻雜於鈦酸鍶中，有助於氧空缺之生成，更進一步提升電導率。La、Nd共摻雜量對鈦酸鍶Seebeck係數並無明顯之影響。x = 0.02試樣具最高之功率因子，於473 K時為1652 μW/mK2。
熱導率方面，隨La摻雜量之減少，有助於降低熱導率，La、Nd共摻雜鈦酸鍶之熱導率，坐落於僅摻La(x =0)及僅摻Nd(x = 0.1)鈦酸鍶之熱導率區間中。
ZT值方面，x = 0試樣於673 K時具最大ZT值為0.19，於573 K溫度以下，x = 0.02試樣於523 K時具最大ZT值為0.15，此值相較於僅摻La之試樣(x = 0)，提升約10%；且相較於僅摻Nd之試樣(x = 0.1)，提升約80%。
關鍵字 : 熱電材料、鈦酸鍶、共摻雜、固相法

In order to enhance the thermoelectric properties of SrTiO3 bulk, La and Nd were co-doped in SrTiO3 in this study. Sr0.9La0.1-xNdxTiO3 (x = 0-0.1) powders were synthesized by solid-state reaction with two-step calcination (at 1200℃ and 1300℃ for 5 h in air). It was pressed into disks by CIP-ing and sintered at 1500℃ for 4 h in forming gas of 5 mol% hydrogen in argon. The microstructure and thermoelectric properties were investigated from room temperature to 673 K. The results of XRD indicated that all samples are of single phase. SEM surface and fracture morphology images revealed that all samples were consisted of similar grains with an average grain sizes of 2-3 μm. The average relative density of all samples was 86%. Electrical conductivity could be effectively improved with appropriate co-doped content (x = 0.02, 0.08) in SrTiO3. However, the Seebeck coefficient was not obviously influenced with different La and Nd contents in SrTiO3. The maximum value of power factor reached 1652 μW/mK2 at 473 K for x = 0.02 sample. With decreasing La content, thermal conductivity decreased. The maximum value of ZT reached 0.19 at 673 K for x = 0 sample. Below 573 K, the maximum value of ZT reached 0.15 at 523 K for x = 0.02 sample, which is much larger than that of other samples, showing that appropriate La and Nd content co-doped in SrTiO3 is a good approach to enhance thermoelectric performance.
Key words: Thermoelectric materials, SrTiO3, co-doped, solid-state reaction

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