Light-Figure Phenomenon Revealed and Crystal Planes Developed by Chemical Etching in Zinc Single Crystals

The light figures revealed by and crystal planes developed on chemically etched zinc crystals may be classified into two main groups and the first group may further be divided into three sub-groups. The IA-group light figures, produced by etching with hydrochloric acid, dilute sulphuric acid, or dilute aqueous solution of ammonium persulphate, consist of the {0001}, {1010} and {1120} light figures, which indicate the development of the {0001} and {101l} planes. The IB・group light figures revealed by etching with concentrated hydrofluoric acid or saturated aqueous solution of cupric chloride involve the {0001} and {1010} light figures, indicating the development of the same crystal planes as the IA group. The IC-group light figures produced by etching with the mixture of saturated aqueous solutions of sodium sulphate and chromic acid anhydride include the {0001}, {1010} and {1120} light figures for a short-time etching and, besides, the {1011} light figure for a prolonged ething, showing that the {0001}, {1010}, {1120} and {1011} planes are developed. The second-group light figures produced by etching with boiling concentrated aqueous solution of potassium hydroxide or of sodium hydroxide contain the {0001}, {1010}, {1120}, {1012}, {1011}, {1126} and {4150} light figures and are associated with the development of the {0001}, {1010}, {1120}, {1012}, {1011}, . {112l} (l≧6) and {4150} planes