抄録
Observations are made on etch pits formed on {100}, {110} and 11111 surfaces and correspond-ing light figures of LiF crystals etched with (1) 47% HF, (2) 2% aqueous solution of NH4OH, (3) 1:1 mixture of 47% HF and glacial acetic acid added with 1% of 1 vol. % HF saturated with FeF3, and 4) and 5)0.01 and 1% aqueous solutions of FeF3, all at 20°C.
The etching with the third and fifth solutions produce characteristic etch pits on {100}, {110} and {111} surfaces. {100} etch pits are sharply pointed and flat-bottomed tetragonal pyramids, of which the former is, while the latter is not, dislocation etch pits. On the other hand, {110} etchh pits are rounded wedges or troughs and {111} etch pits are rounded triangles, whose-correspondence to dislocations are not evident owing to their smallness in size. The second solution reveals {100} etch pits of a square form of which the reproducibility is poor, but the alternating etch with the first and second solutions produces clear-cut {111} etch pits of a triangle pyramid form, which are not dislocation etch pits.
The observed light figures vary diversely with the shape, size, and distribution of etch pits. It has been found that {100} and {110} light figures in particular, which are revealed by etching with the third and fourth solutions, are so distinct as can be applied for the accurate orientation determination.
