本研究利用固態反應法製備計量比不同之鍺酸鑭 (La10-xGe6O27-1.5x，x = 0、0.25、0.5、0.75、1)，探討晶體結構與電性之間的關聯，並模擬間隙氧在結構中的移動路徑。
實驗結果顯示 1200°C/3 h 的煅燒條件下，所有成分點皆可合成單一相的鍺酸鑭，透過 PDF卡號比對，LGO9、LGO9.25、LGO9.5 為六方晶系 (P63/m)，而 LGO9.75、LGO10 繞射峰數目變多，經比對後屬於三斜晶系的繞射峰，透過晶格常數精算，三軸長度 (a、b、c) 與夾角 (α、β、γ) 皆不相等，結構為三斜晶系 (Pī)。透過高溫 XRD 分析，六方晶系成分點在 500°C -800°C 繞射峰無明顯變化，而三斜晶系成分點繞射峰數目有變少的趨勢，其中 LGO9.75 在 600°C - 700°C 已由三斜晶系轉為六方晶系；而 LGO10 並未發生相轉換，結構仍維持三斜晶系。本研究模擬出 5 條間隙氧移動路徑，其中 1 條繞著鍺氧四面體在結構中穿梭；另外 4 條則是繞著通道氧移動，但所有間隙氧移動路徑皆沿 c 軸以類正弦模式傳遞。六方晶系成分點之導電率、間隙氧移動空間皆大於三斜晶系成分點，且導電率與間隙氧移動空間呈正相關，代表間隙氧移動空間越大，導電率越高。

Apatite structures have the highest conductivity of all solid oxide fuel cell (SOFC) electrolytes because of their conduction mechanism. Among all apatite-type electrolytes, lanthanum germanates possess the highest conductivity. To observe the relationship between composition, crystal structure, and ionic conductivity, lanthanum germanates (La10-xGe6O27-1.5x, x = 0, 0.25, 0.5, 0.75, 1) were synthesized using the solid-state method. The XRD pattern showed that a single phase could be obtained for all compositions calcined at 1200°C/3 h. Crystal structure analysis using the Rietveld refinement approach indicated that x = 0.5, 0.75, 1 has a hexagonal structure (P63/m, #176) and x = 0, 0.25 has a triclinic structure (Pī, #2). These results show that five migration pathways could be established, assuming the interstitial oxygen passes the larger opening within the crystal structure. These five migration pathways are sinusoid-like three-dimensional routes along the c-axis. Since x = 0, 0.25 transforms to a triclinic phase, the migration opening becomes narrower and lowers the ionic conductivity. The Arrhenius plot of x = 0.25 demonstrated a sharp decrease in activation energy, indicating that the phase transition from triclinic to hexagonal occurred at around 650°C.

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