Micromorphological instability of a growing face as a source of oscillatory zoning in crystals

Abstract

AbstractOscillatory zoning in solid solutions of alums ((K,NH4)Al(SO4)2·12H2O, K(Al,Cr)(SO4)2·12H2O, (K,Rb)Al(SO4)2·12H2O) and nitrates of divalent metals ((Sr,Pb)(NO3)2, (Ba,Pb)(NO3)2) grownfrom low-temperature aqueous solutions is considered. The zoning is detected by means of X-ray diffraction topography, crystal optics and electron probe microanalysis and involves variations of the crystal composition and degree of the growth ordering of atoms. The zoning patterns are very different in the predominant ﹛111﹜ and ﹛1̄11﹜ and subordinate ﹛100﹜ and ﹛110﹜ growth sectors. The different types of micromorphological instabilities of a growing face are suggested to explain the origin of the observed zoning.