本研究探討焦磷酸鈰（CeP2O7）在不同溫濕度下之質子導電性，希望能應用於操作溫度200℃~400℃燃料電池之電解質。近年來由於報導相關磷酸鹽（CsH2PO4、Sn0.9In0.1P2O7）在此溫度範圍下有較佳的質子導電率，使得磷酸鹽的固態電解質應用可能性急遽增加，尋找具有充份質子導電率且耐熱的電解質為此溫度範圍燃料電池的關鍵性議題。
本實驗使用CeO2與85%H3PO4 藉由低溫合成法合成CeP2O7粉末，製作未燒結後（300℃、450℃）、燒結後（300℃∼900℃）試片，測量質子導電率與操作溫度之關係。
結構分析方面，取單一相煅燒300℃之CeP2O7，其高解析的X-ray繞射圖，經由 Rietveld 方法進行精算，得到CeP2O7結構參數，精算結果顯示，CeP2O7結構為類立方體(Quasi-cubic)，空間群為P 1，晶格常數為a=8.5584 Å，b=8.5597 Å，c=8.5767 Å，α=90.17°，β=90.03°，γ=89.85°，晶體密度為3.304 g/cm3。
高濕度氣氛下（PH2O=0.114 atm），燒結300℃之焦磷酸鈰，操作溫度在200℃時，最高質子導電率為1.87×10-2 S cm-1 ; 燒結450℃的焦磷酸鈰，操作溫度在180℃時，最高質子導電率為3.0×10-2S cm-1 ; 燒結溫度高於600℃之後，質子導電率均低於1×10-2 S cm-1。焦磷酸鈰摻雜10%鎂(Ce0.9Mg0.1P2O7)，燒結450℃，操作溫度在200℃時，質子導電率高達4.0×10-2 S cm-1，且在更高溫度範圍下(200℃~260℃)，質子導電率均超過0.1 S cm-1 。

This study investigates the dependence of proton conductivity on temperature, humidity, sintering temperature, and dopant content of the cerium pyrophosphate, and the feasibility of cerium pyrophosphate as the electrolyte for the fuel cell operated in 200 – 400 C. Recently, the literature reports on the proton conductors of phosphates, such as CsH2PO4 and Sn0.9In0.1P2O7, have demonstrated their proton conductivities reaching the electrolyte application level in this temperature range. Hence the probability of building a proton power fuel cell with a phosphate electrolyte has escalated. On building a fuel cell operated in this crucial temperature range, it is critical to find an enduring electrolyte with sufficient proton conducting capability.
We synthesized the CeP2O7 powder using the powder of CeO2 an 85% phosphoric acid (H3PO4), and found the maximum synthesis temperature was an important factor for the proton conductivity. Our specimens include the unsintered, pressed pellets which were calcined at 300 and 450 C, and the sintered pellets which were sintered at 300 – 900 C. On the structure characterization, the powder diffraction patterns resulted from low temperature synthesized powder were used to refine the CeP2O7 crystal structure with Rietveld refinement method using the GSAS software. Starting with a cubic cell of space group P a , the refinement results indicate that a triclinic (pseudo-cubic) cell with space group P1 is a better model, and the refined lattice parameters, a=8.5584 , b=8.5597, c=8.5767.
The pyrophosphate of (Ce0.9Mg0.1)P2O7 calcined at 300 C and sintered 450 C has been identified as the specimen most suitable for the electrolyte application of 200 – 400 C proton power fuel cells. The proton conductivity of (Ce0.9Mg0.1)P2O7 has been demonstrated over 0.01 S cm-1 in the temperature range of 200 - 260 C under the atmosphere of water vapor pressure 0.114 atm. Its maximum conductivity is 4.0  10-2 S cm-1 at 200 C, further increasing temperature decreases the conductivity. The undoped CeP2O7, calcined at 300 C and sintered 450 C, also exhibits high proton conductivity, but in a lower temperature range. The conductivity of CeP2O7 at PH20=0.114 atm exceeds 0.01 S cm-1 at 120-180 C, with its maximum 2.98  10-2 S cm-1 at 180 C.

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