摘要:
A tetragonal system tunnel-structured compound having the formula:A.sub.x [Ga.sub.8 M.sub.y Ga.sub.(8+x)-y Ti.sub.16-x O.sub.56 ](I)wherein A is at least one alkali metal selected from the group consisting of K, Rb and Cs, or a solid solution of such alkali metal with lithium, sodium or barium, M is at least one trivalent metal selected from the group consisting of Al, Fe and Cr, x is a number of from 0.1 to 2.0, and y is a number of from 0 to 10.