鎳酸鑭屬於無能隙之氧化物導體，雖然具有很高的電導，但因載子濃度過高，而使席貝克係數偏低。根據前人研究結果，鎳酸鑭的導帶寬度可藉由摻雜稀土元素或改變氧計量比予以調整：摻雜之離子半徑愈小，導帶寬度則愈窄，直至鎳酸鑭中氧的2p 價帶軌域與鎳離子的d 導帶軌域分離，出現能帶間隙；而氧空缺的增加亦有類似效果。因此可以藉由摻雜稀土元素或調控氧空缺來優化電導和席貝克係數，以提升功率因子。
本研究企圖透過摻雜稀土元素銪及釔來調整鎳酸鑭的導電和熱電特性，而試片合成方法為溶膠－凝膠法，合成條件為大氣下、溫度800 oC、燒結時間24小時。根據成分及結構分析顯示，摻雜銪及釔之鎳酸鑭試片中皆有氧化鎳二次相析出，且析出量會隨著摻雜比例增加而增多。電性分析顯示，鎳酸鑭之電導確實因摻雜銪或釔而降低，此結果與預期相符，因為銪及釔的離子半徑皆比鑭小。但是熱電分析顯示，席貝克係數因摻雜銪及釔而隨之降低，與預期結果不符，原因可能與試樣中存在氧化鎳二次相有關。鎳酸鑭中主要電荷載子為電子，而氧化鎳為p 型半導體，其存在會造成雙載子效應，降低席貝克係數。所有試片所測之席貝克係數均為負值，約為-4 ~ -13 μV/K，這意指多數電荷載子仍為電子。本研究結果顯示，去除鎳酸鑭中的氧化鎳二次相是提升其熱電特性的關鍵。

LaNiO3 (LNO) is an oxide conductor without a band gap. So, it has a very good electric conductivity, but its carrier concentration may be too high to have a large Seebeck coefficient. It was reported that the conduction band width of rare-earth (RE) nickelates decreases with the decrease of the RE ion size and in small RE nickelates, there was a separation between the conduction and valence bands. This provides some room for bandgap engineering to optimize the carrier concentration, so that a good trade-off may be achieved between the good electric conductivity and large Seebeck coefficient. So, in this study, Eu and Y substituted LNO samples were synthesized by the sol-gel method and their electric and thermoelectric properties were assessed. The results showed that it was very difficult to prepare the substituted LNO samples with a high phase purity and NiO was one of the secondary phases often observed in the samples. As expected, the partial substitution of La ions with smaller Eu or Y ions resulted in a reduction in the electric conductivity. However, against the expectation the Seebeck coefficient was also reduced by either Eu or Y substitutions. The cause may be ascribed to the secondary phase NiO observed in the samples, which is well known to be a p-type semiconductor. Because LNO itself has the n-type charge carriers, the dual-type charge carrier problem may eventually nulls the effect of the bandgap engineering. The result indicates that the crucial step in improving the thermoelectric property of the LNO based oxides is to eliminate the secondary phase of NiO.

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