A preliminary electron microscope study of chemical twinning in the system MnS+Y₂S₃, an analogue of the mineral system PbS+Bi₂S₃(galena + bismuthinite)

Abstract

Abstract Examination in the electron microscope of various mixtures of MnS and Y2S3 after heating confirms the existence and structures of the phases MnY2S4 and MnY4S7. It also reveals the existence of at least one phase intermediate between these two, viz. Mn2Y6S11 whose structure is an ordered intergrowth of the other two intermediate phases. Low proportions of Y2S3 produce isolated {113} twin planes in a B1 type matrix, and these tend to aggregate into thin lamellae (domains) of MnY2S4. Thus the twin plane is a structural unit in all cases (as previously forecast), and may occur in an ordered or disordered fashion. The necessity for a ‘cation-vacancy’ model is therefore minimized, or even eliminated.