New fluoride ion conductor, K_xBi_1-xF_3-2x (.02≤ x ≤.12), with the tysonite structure

A study of the phase relationships in the KF-BiF3 system shows the existence of a new compound occurring in the composition range from about 3 to 10 mole percent KF. X-ray analysis of this compound showed it to be isomorphous with the trivalent rare earth fluorides having the tysonite structure. This compound has been characterized by X-rays, lattice parameter and density measurements, DTA and chemical analysis. Ionic conductivity measurements on both single crystals and pressed pellets in the temperature range from 25 to ∼ 450°C show it to be an excellent fluoride ion conductor. © 1981.