The possibility of inducing rotational growth striae with a small period in barium sodium niobate crystals (BSN) is examined. Crystals grown had a period stability up to 1 percent and were suitable material for anisotropic light diffraction by ferroelectric domains.However intense striae were produced only for periods 1 > 5 pm. With the help of Bragg optical diffraction by growth striae the diffusion coefficient D in solid phase responsible for striae smoothing during annealing was measured. The magnitude D = 10-l1 om2 s-1 at the meIting point was obtained. Such D value leads to the vanishing of striae with il < 5 pm in BSN crystals during growth. PaCCMOTpeHa B03MOXHOCTb @OPMHPOBaHHR BpaUaTeJIbHbIX CJIOeB POCTa C MaJIbIM IIepEi OHOM B KpEicTaJInax HEiO6aTa 6apEiR-HaTpMR (BHH). BbIpaUeHHbIe KpEiCTaJIJIbI HMeJIH CTa6EiJIbHOCTb IlepEiOHa a0 1 % Ei Il03BOJIHJIEi OCyUeCTBEiTb aHH30TpOIIHYH) En-6 b m~ IIOJIyseHbl JIHIIIb AJIR IIepEiOHOB 1 > 5 MKM. MeTOnOM 6p3rro~c~ofi HH@paHqEiH CBeTa Ha CJIOFIX POCTa Ei3MepeH K03@@HUHeHT AEi@@y311H D B TBepHOfi G.838, OTBeWiIoUEifi D T"N 10-l' CMZ/C HJIH TeMIIepaTypbI IIJIaBJIeHEiR. TaKaR BeJIEiWiHa IIPEiBOAEiT K MC4e3HO-BeHHH) CJIOeB C @paKqEim cBeTa Ha c e r~e~o m e~~p~~e c~~i x HoMeHax. OnHaxco nHTeHcmBHbie C~O H pocTa paccacnsaHEim cnoeB B npoqecce oTmEira HpEicTannos BHH. IIonyseHo 3~a~e~~e > 5 MKM yme BO BpeMR BbIpaUtlBaHEiR KpllCTaJrJIOB EHH.