Аннотация:A detailed knowledge of the morphology of crystallites ina finely divided powder is required in many fields ofmaterials science. The purpose of this work was todetermine the crystallite-size distribution function inY3 Fe 5 o 12 , Bi 2W0 6 , LiNb03 powder strain-free materialsprepared by the hydrolysis of alkoxides. In order tostudy the crystallite-size variation, X-ray diffractionexperiments ( DRON-J diffractometer, CUK 0 l >!ere combinedwith electron microscopy and second harmonic generationmethods. The Tikhonov's regularization procedure toFourier X-ray line profile analysis was applied forcalculation of domain-size distribution function.Instrumental broadening was obtained from standardspecimens of the same composition. All calculations wereperformed by the special computer program which we haveadapted to the ES-IOJJ computer. The effective domainsize shows a tendency to increase with heating and has amaximum in the temperature range 600-70o'c. Above thistemperature range the crystallite size does not varyappreciably. There is a reasonable agreement between theeffective domain sizes obtained from X-ray profileanalysis and by other physical methods up to 1000 A. Theparticles detected by electron microscopy in the 1000 Ato 1500 A diameter range are not monocrystalline for thegreater part. The values of crystallite size arecomputed for several crystallographic directions. Theshape of crystallites is anisotropic at low temperaturebut the isotropy increases on heating.