Zinc sulphide has a high-temperature stable structure at T>1024℃

i.e.wurtzite(2H)and a low-temperature stable structure at T<1024℃

i.e.sphalerite(3C).Much x-ray diffraction study of 2H→3C structure transformations were reported

but the study of 3C→2H structure transformations are little.Especially

the experimental investigations about the orientations of 3C→2H transformations by Laue diffraction haven't been seen as yet.In the present work

the stacking faults were introduced into 3C-ZnS single-crystals by heat treatment

the orientated relation of 3C→MT(micro-twin)→2H transformations was then investigated with Laue back reflection method.Specimens of ZnS single-crystals were prepared with vapour-grown method.It was found by means of x-ray diffraction that the crystallinity of the specimens is fine

and there is no stacking faults in ZnS crystals.The heat treatment condition.1100℃

S vapour protecting the specimens

keeping crystals at high temperature 10 minutes to 5 hours

cooling the specimens in air.The x-ray condition.Cu radiation

35kV

D=37mm

taking Laue back reflection photographs of each specimen in fixed position before and after each heat treatment respectivly.After that

a lot of new Laue diffracted patterns which have not been reported in the literature were observed.In order to interpret these patterns

simple and suitable formulas to index Laue photographs and calculate "anomalous diffracted spots" have been derived

and the stereographic projections corresponding to some crystal planes also have been plotted.All of Laue diffracted spots and streaking in the Laue photographs were indexed and analysed.