Oxygen Apatite Ion Conductor Preparation And Performance

Fuel cell is a kind of equipment which converts the chemical power into theelectric power directly. As the third generation of fuel cell, the solid oxid fuel cell(SOFC) developed fastly among all kinds of fuel cells. As the important part of SOFC,the electrolyte has the fuction of transfering the ions between the electrodes. Up to now,most researches are on electrolytes based on doped YSZ, CeO₂, Bi₂O₃ and so on.Recently, the oxyapatite as the solid electrolyte attracts much attention. In thisarticle, we described the work mechanism of SOFC and the application of thiselectrolyte in SOFC, narrated the structure, characters of oxyapatite and the problems ofapplication in SOFC. The synthesis methods, conduction mechanism and recentprogress of oxyapatite have also been summarized in the thesis. The relation of thecomposition, structure and conduction were summarized. In this work, we obtained thevanadium oxyapatite and germanium oxyapatite, respectively by the solid state method,studied the effect of dopping in M or T site on their electric properties, so that we couldfind the relation between the sructure and the conduction mechanism. We synthesizedthree kinds of oxyapatite, M₁₀(TO₄)₆O₂, M₁₀(TO₄)₆O_2+x, M₁₀(TO₄)₆O_2-x. It was foundthat the most important factors to determine the oxygen ionic conduction are the amountof interstitial oxygen, the amount of cation vacancies, ionic radius and density ofceramics. Among these samples, the highest one is La_9.45(GeO₄)_5.5(PO₄)_0.5O₂, which is8.29×10^-3 Scm^-1 at 700℃in air.