三價離子摻雜於電解質BaZrO3的導電趨勢

Abstract

本實驗為探討BaZr1-xMxO3， (M = In3+、Y3+、 Yb3+、 Dy3+、 Gd3+、 Sm3+、 Nd3+、 La3+)不同摻雜金屬的導電趨勢，並利用計算的結果去解釋。實驗部分為使用燃燒法合成不同濃度的摻雜金屬，並使用XRD、SEM、EDX、ICP-MS來確認物理及化學性質。再把粉末壓錠，並燒結於1250、1450、1600 ℃，持溫5、10、40小時，形成BaZr1-xMxO3 試片，進行導電度測試，通入氣氛為濕-空氣、濕-氫氣、乾-氮氣、乾-氫氣。 計算部分為使用密度泛涵理論(DFT)計算摻雜於BaZrO3的氧空缺(V_o^(..))及氫缺陷的形成能以及氧空缺、氫缺陷、氫氧空缺移動的反應熱。 由實驗及計算的結果顯示，導電率會隨著摻雜的濃度增加或持溫時間降低而上升，燒結溫度對導電率的影響則不大。從化學的觀點來看，導電率會受到摻雜金屬的離子半徑所影響，較小的離子半徑，導電率佳，且計算出來的反應熱低。

Trends of the ionic conductivity of BaZr1-xMxO3, (M = In3+, Y3+, Yb3+, Dy3+, Gd3+, Sm3+, Nd3+, La3+) have been experimentally and computationally examined in this work. Experimentally, the powder with different dopant ratios , 2%, 5%, 10% and 20%, has been initially synthesized by GNP (glycine nitrate process) method, and it physical and chemical properties have been examined by XRD, SEM, EDX and ICP-Mass (Inductively coupled plasma mass spectrometry). The synthesized powder is further pressurized and sintered at different temperatures, 1250, 1450 and 1600 oC and heating period, 5, 10 and 40 hours, to form BaZr1-xMxO3 pellets for the conductivity tests in various atomspheres: dry N2, dry H2, wet air and wet H2. Computationally, formation energies of oxygen vacancy V_o^(..) and proton defect OH_o^' and enthalpy of V_o^(..) migration, proton hopping and OH_o^' diffusion of the doped BaZrO3 have been systematically examine by the means of density functional theory (DFT) calculation. Based on the experimental and computational works, the results show that the ionic conductivity will increase as the dopant ratio raises and the sinter period decreases. The sinter temperature has limited effect on the conductivity. From the chemical aspect, the conductivity is systematically influenced by the ionic radius of the doped cation. The small radius of the dopant results a better conductivity from the experimental measurement and lower enthapy in the DFT calculation.