Perfect pure (concentration of donors ~ 10,6cm ") single crystals with joint polytypes (hexagonal-cubic) or heterojunction investigated using low temperature (4.2 K and 77 K) photoluminescence. Phase transformation started exactly from lamella between polytypes,[alfa]-[beta](3C - 6H) SiC transformation distributes from lamella as from nuclear. Photoluminescence spectra are similar to the spectrum demonstrated by pure perfect 3C-SiC crystal in the field of mechanical deformation. In the zone of joint polytypes and zone of the plastic deformation in perfect 3C-SiC crystal after bending, the same stacking faults are localized. Luminescence in the disordered u-zone as a result of phase transformation is represented by a set of intensely pronounced stacking fault spectra. These spectra reside on more or less intense background band, which are emission of the donor-acceptor pairs in SiC. Excitation luminescence spectra confirm appearance of stacking faults which are responsible for metastable intermediate micro- and папо-SiC structures. Solid-phase transformations ,[alfa]?[beta] (i are related with the same intermediate metastable microstructure that take place in the transformation ,[alfa]-[beta].
