Multi-valent Cation Conductors and their Application for Electrochemical Use

研究结果表明：（1）YPO_4具有锆英石型晶体结构，是一种立体化学粗糙的晶体结构。虽然该化合物不包括二价阳离子，但如果钙作为磷酸盐掺杂，则晶体可以包含间隙钙离子，其对钙离子传导起重要作用。在800 ° C时，电导率为5x10 ^Scm ^。<-3><-1>在镁的情况下，得到类似的结果。但镁离子电导率不如钙离子电导率高。在钒酸盐和砷酸盐固溶体中，虽然它们具有几乎相同的晶体结构，但没有观察到二价离子导电。(2)具有应变NaCl型结构的硫酸钙显示钙离子传导，如果掺杂另一种化合物，则意图形成间隙钙离子。含有5 m/o过量钙的样品在1000 ℃下的电导率为3 × 10 - 4 Scm-4。<-3><-1>通过掺杂Al_2（SO_4）_2也可以在基质晶体中引入钙离子空位。在这种情况下，观察到类似的导电行为，但是导电率本身相对较低。(3)用二价阳离子取代传统碱金属离子导体中的碱金属离子，只有在斜方沸石体系等特殊情况下才能得到阳离子导体。然而，这些是不稳定的，并且易于在较低温度范围内分解成两相。(4)考虑到电池结构的电动势响应和电解时钙化合物的形成，本研究发现的离子导体有可能电化学地用作电解质。

The results of this study are summarized in the followings, (1) YPO_4 shows a zircon-type crystal structure, which is a stereochemically rough one. Although this compound includes no divalent cation, if calcium is doped as a phosphate, the crystal can contain the interstitial calcium ion, which plays an important role for the calcium ion conduction. The conductivity is 5x10^<-3>Scm^<-1> at 800ﾟC. In the case of magnesium, the similar result is obtained. But the magnesium ion conductivity is not so high as the calcium ion conductivity. In the solid solutions based on vanadate and arsenate, di-valeut ion conduction is not observed, although they have almost the same crystal structure.(2) Calcium sulfate, having a strained NaCl-type structure, shows calcium ion conduction, if another compound is doped intending formation of interstitial calcium ion. The Conductivity of the sample including 5 m/o excess calcium is 3x10^<-3>Scm^<-1> at 1000ﾟC. We can also introduce calcium ion vacancy to the host crystal by doping of Al_2(SO_4)_2. In that case, the similar conduction behavior is observed, but the conductivity itself is relatively lower.(3) If we substitute divalent cations for alkali ions of the conventional alkali ion conductors we can obtain cation conductor only in the special case such as ramsdellite-based system. However, these are unstable and apt to decompose into two phases at lower temperature ranges.(4) The ionic conductors found on this study are possible to employ electrochemically as electrolytes, considering emf response on construction of cell and formation of calcium compound on electrolysis.