本研究主要探討兩種氧化物熱電材料，包含n型的鎳酸鑭（LaNiO3）與p型的鉍銅硒氧（BiCuSeO）。鎳酸鑭是以溶膠–凝膠法製備，並通過對製程參數的控制，達到奈米晶粒結構。於燒結溫度500 C時，樣品中有氧化鎳和氧化鑭等雜相出現，提高燒結溫度至600 C時可得到純相之鎳酸鑭，晶粒大小為18 nm。若再提高燒結溫度至700 C以上時，於晶界區域會出現微小的析出物，經分析後確定為氧化鎳。於燒結溫度600~800 C製備之試片，其電阻率皆隨著量測溫度的增加而上升，表示此材料具有金屬導電特性。將溶膠鍍膜並置於不同的氣氛下（空氣、氧氣、氬氣）成長鎳酸鑭薄膜，探究其導電性與化學穩定性，結果顯示於氧氣下燒結可得到最佳之電阻率4.65×10-4 Ω-cm。成長於鋁酸鑭之磊晶薄膜，受壓縮應力影響，其氧空缺較少，電導率較高；成長於鈦酸鍶之磊晶薄膜，受拉伸應力而使得c軸受到壓縮，相當於給薄膜加壓，因而在高溫高真空中，化學穩定性最好，其脫氧速率最慢。西貝克係數的分析結果顯示，所有試片均為負值，室溫值約為-12 ~ -15 μV/K，顯示鎳酸鑭的多數電荷載子為電子，此結果亦被霍爾分析所證明。將鎳酸鑭摻雜氧化鎳並分析其性質，摻雜後雖然西貝克係數由-23 μV/K提升至-50 μV/K (550 K)，但是電阻率亦上升兩個數量級。不同燒結溫度之樣品測量其熱傳導率，數值在室溫時為0.580 ~ 0.886 Wm−1K−1，並隨燒結溫度上升而有些微增加。根據優化後的電導率、西貝克係數和熱傳導率計算所得之熱電優值（ZT），於量測溫度550 K時可達到0.034，經由擬合後推估在量測溫度1000 K時可達0.15，可媲美氧化鋅、鈦酸鍶等n型氧化物熱電材料。
p型之鉍銅硒氧熱電材料，西貝克係數較大，惟其電導仍有改善空間，因此提高電荷載子濃度是進一步提升ZT值的關鍵。本實驗是以固相燒結法在流動的氬氣氛中製備鉍銅硒氧，於燒結溫度550〜750 C時可得到純相之樣品，若再提高燒結溫度至850 C以上，則會分解出Cu2Se雜相。純相之鉍銅硒氧測得室溫電導率為2.88 S/cm，當鉍銅硒氧摻雜30 %的鈣後，其室溫電導率可提升至204 S/cm，但是其西貝克係數亦由290 μV/K下降至94 μV/K。此外，本研究利用X光電子能譜對鉍銅硒氧中各元素的價態，以及摻鈣後的變化進行了詳細分析。除了預期的Bi3+和Cu1+外，在未摻雜的鉍銅硒氧樣品中還偵測到Bi2+和Cu2+，而在摻雜Ca的樣品中發現有Bi4+、Cu2+和Cu3+。Ca被證實僅以2+價態存在，而Se的3d鍵結能譜出現兩個峰值，經由比對數據資料庫後發現，其中的一個常見於含Se之介金屬化合物，而另一個常見於含Se之氧化物，因此研判Se不僅和Cu有鍵結，Se和O之間也存在某種程度的鍵結。從觀察到的元素價態，可以了解未摻雜及摻鈣之鉍銅硒氧中的電荷補償機制以及p型載子的來源。本實驗數據顯示p型載子的來源除了其他研究團隊建議的Cu空缺外，應該還有Cu2+和Cu3+。

LaNiO3 was synthesized by the sol-gel process in both bulk and thin film forms. Nanostructured bulk samples of a pure phase were obtained by sintering at 600 C. The chemical stability and its influence on the electric conductivity at high temperature were studied using the LaNiO3 films grown on the Si, LaAlO3 and SrTiO3 substrates. The compressive epitaxial film on LaAlO3 showed highest conductivity of 4.65×10-4 Ω-cm owing to the least amount of oxygen vacancy. The stretched epitaxial film on SrTiO3 showed best chemical stability with the lowest oxygen loss rate in vacuum, which was benefited from the extra pressure imposed by the shrinkage of the c-axis. LaNiO3 had the n-type charge carrier and showed a negative Seebeck coefficient (S) of about -15 μV/K at 300 K. NiO was added to LaNiO3 to form a composite, which showed an increased S of -50 μV/K at 550 K. However, the electric conductivity was also reduced by two orders of magnitude by the NiO addition. The thermal conductivity of bulk LaNiO3 increased with the sintering temperature, ranging between 0.580 to 0.886 Wm−1K−1 at 300 K. With the optimized S and electric and thermal conductivities, thermoelectric figure of merit (ZT) was calculated to be 0.034 at 550 K and may rise to 0.15 at 1000 K.
Bi1-xCaxCuSeO (x=00.3) was sintered at 650 C in an airtight system flowing with argon. The composition and phase purity were confirmed by the energy dispersive X-ray spectroscopy, X-ray diffraction and transmission electron microscopy. Electric and thermoelectric measurements showed that the Ca doping resulted in an increase in p-type carrier concentration and therefore, an increase in the electric conductivity. This was accompanied by a reduction in the Seebeck coefficient. However, the overall result of the Ca doping was the increase in both the power factor and the ZT value. X-ray photoelectron spectroscopy was carried out to check the oxidation states of elements in Bi1-xCaxCuSeO, based on which the charge compensation mechanisms were proposed. The results indicate that the p-type carriers in Bi1-xCaxCuSeO may be correlated to the higher oxidation states of Cu ions (i.e. Cu2+ and Cu3+).

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