Five new polytypes and polytypic change in PbI₂

Five new PbI₂ polytypes, 8H(1232), 10H(11112112), 10H(112222), 22H[11(22)₅] and 30R[111313]₃, were solved by the X-ray diffraction method. It was found on polytypic change that (a) the 2H polytype is changed into various polytypes on heating at 130°C and most of these further change to 12R[13]₃ on heating at 260°C; (b) the polytypes 4H, faulted 4H, 14H, 22H, 26H and 30R with layer structures similar to the 12R[13]₃ are fairly stable at high temperatures; (c) the 2H-30R [111313]₃ transformation occurs reversibly.