STUDY ON AMMONIUM POLYPHOSPHATE PROTON CONDUCTORS AS ELECTROLYTES FOR NOVEL INTERMEDIATE TEMPERATURE FUEL CELLS

聚磷酸铵（NH_4PO_3）具有很高的质子传导率，是一种很有前途的中温燃料电池电解质材料。通过添加合适的基质材料和铵离子的部分取代，提高了聚磷酸铵的热稳定性。(NH以<13>NH_4 PO_3/（NH_4）_2SiP_4O为基体，制备了NH_4PO_3/（NH_4）_2SiP_4O<13>复合材料。复合物（4：1）在300℃下具有5.4mS·cm ~（-1）的高质子电导率<-1>，并具有改善的热稳定性。质子电导率随着基质含量的增加而增加。而摩尔比大于8：1的NH_4PO_3/（NH_4）_2SiP_4O_3<13>复合材料在300℃时不稳定，尤其是在潮湿气氛下。因此，在实际应用中，摩尔比低于8：1的复合物是优选的。(NH_4）<1-x>制备了K_xPO_3固溶体，以提高其热稳定性。(NH_4）_<0.2>K_PO_3<0.8>在400℃时仍保持固态，具有较高的质子电导率。在这些固溶体中，NH_3在加热过程中被消除，并发生相分离，形成KPO_3晶相和HPO_3非晶相。前一相具有高的热稳定性，并作为基质。后一阶段在质子传导中起着至关重要的作用。

Ammonium polyphosphates (NH_4PO_3) have high proton conductivity, end are promising materials as electrolytes in intermediate temperature fuel cells operated at around 300℃. In the present study, thermal stability of the ammonium polyphosphates was improved by adding suitable matrix materials and by partial substitution of ammonium ion.(NH_4)_2SiP_4O_<13> was added as a matrix to form NH_4PO_3/(NH_4)_2SiP_4O<13> composites. The composite (4:1) gave a high proton conductivity of 5.4 mS cm^<-1> at 300℃ with improved thermal stability. The proton conductivity increased with an increase in the content of the matrix. However, NH_4PO_3/(NH_4)_2SiP_4O_<13> composites with molar ratio greater than 8:1 were not stable at 300℃, especially under humidified atmosphere. Hence, the composites with molar ratio lower than 8:1 are preferable in practical use.(NH_4)_<1-x>K_xPO_3 solid solutions were then prepared to improve thermal stability. (NH_4)_<0.2>K_<0.8>PO_3 kept a solid state even at 400℃ and gave a high proton conductivity. In these solid solutions, NH_3 was eliminated during heating and phase separation into a crystalline phase of KPO_3 and an amorphous phase of HPO_3 occurred. The former phase has a high thermal stability and works as a matrix. The latter phase plays an vital role in proton conduction.