Ion Exchange in Alkali Layers of Potassium β ‐Ferrite ((1 + x)K ₂ O · 11Fe ₂ O ₃ ) Single Crystals

The potassium ions in potassium β‐ferrite ((1 + x)K 2 O ·11Fe 2 O 3 ) crystals were exchanged with Na + , Rb + , Cs + , Ag + , NH 4 + , and H 3 O + in molten nitrates or in concentrated H 2 SO 4 . On the other hand, spinel and hexagonal ferrites were formed by soaking the crystals in the melt of divalent salts. The crystals of K + , Rb + , and Cs + β‐ferrites decomposed to form α‐Fe 2 O 3 at high temperatures of 800° to 1100°C. In addition, H 3 O + , NH 4 + , and Ag + β‐ferrites decomposed to form α‐Fe 2 O 3 at relatively low temperatures of 350° to 650°C, in accordance with the stabilities of the inserted ions. The electrical properties of some β‐ferrites were measured.