Sr 함량이 Cu-doped LSM(La1 − xSrxMn0.8Cu0.2O3)의 구조적변화와 전기전도도에 미치는 영향
Structural change and electrical conductivity according to Sr content in Cu-doped LSM (La1 − xSrxMn0.8Cu0.2O3)
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La1 − xSrxMn0.8Cu0.2O3 − δ(LSMCu)에서 Sr 함량에 따른 구조적 변화와 전기전도도에 대해 연구, 고찰하였다. EDTA citric complexing process(ECCP)로 페로브스카이트 구조를 갖는 La0.8Sr0.2MnO3(LSM)와 La1 − xSrxMn0.8Cu0.2O3(0.1 ≤ x ≤ 0.4)을제조하였다. Sr 함량이 증가할수록 격자상수와 격자부피는 감소하는 경향을 나타내었으며, 이는 Sr 함량이 증가함에 따라B-site에서 증가하는 Mn4+ 이온과 Cu3+ 이온의 영향인 것으로 판단하였다. 0.1 ≤ x ≤ 0.3 범위의 조성에서 Sr 함량이 증가할수록 500~1000oC에서 측정된 전기전도도는 증가하였고, x = 0.3 조성에서는 750oC와 950oC에서 각각 172.6 S/cm와 177.7 S/cm (최고값)를 나타내었다. 반면, x = 0.4 조성에서는 전기전도도가 감소하였는데 이는 입계에 발생한 산화물에 의한 영향으로판단하였다. Sr 함량이 증가함에 따라 B-site에 존재하는 Mn4+ 이온과 Cu3+ 이온의 증가로 인해 격자수축이 발생하고,hopping mechanism에 관여하는 charge carrier들이 늘어나 전기전도도가 증가한 것으로 판단하였다.
Abstract
The structural change and the electrical conductivity with Sr content in La1 − xSrxMn0.8Cu0.2O3 (LSMCu) were studied. La0.8Sr0.2MnO3 (LSM) and La1 − xSrxMn0.8Cu0.2O3 (0.1 ≤ x ≤ 0.4) were synthesized by EDTA citric complexing process (ECCP). A decrease in the lattice parameters and lattice volumes was observed with increase of Sr content, and these results were attributed to the increasing Mn4+ ions and Cu3+ ions in B-site. The electrical conductivity measured from 500oC to 1000oC was increased with increase of Sr content in the 0.1 ≤ x ≤ 0.3 composition range, and it was 172.6 S/cm (at 750oC) and 177.7 S/cm (at 950oC, the maximum value) in x = 0.3. The electrical conductivity was decreased in x = 0.4because of the presence of the second phase in the grain boundaries. The lattice volume was contracted by increase of Mn4+ ions and Cu3+ ions in B-site according to increase of Sr content and the electrical conductivity was increased with increase of charge carriers which were involved in the hopping mechanism.
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