Optical observations and electrooptic effect of NH4Cl near its order-disorder phase transition
Résumé
Observations of slip bands parallel to {100} planes are described and it is shown that they induce inhomogeneous internal stresses which play an important role in the nucleation process at the order-disorder phase transformation. The heterophase structure at the phase coexistence consists of slabs parallel to {111} planes. The phase transformation involves large internal stresses which result in plastic deformations.We present also the first measurements of the temperature dependence of the electrooptic coefficient r14 inside one domain, and compare it with previous measurements of the piezoelectric effect.