Growth defects in barium‐strontium niobate crystals

Abstract

The paper is concerned with the results of investigation of barium-strontium niobate chemical composition change, of the lattice parameter, microhardness of the crystal region. Analysis reveals the increase of the barium content up to 4% and the change of the crystal lattice parameter by 8, leading t o considerable tensions and crystal cracking. The etching of the slides perpendicular to the growth axis has been realized as well as the decoration of the fresh cleavages by anthraquinone vapours which indicate the electric inhomogeneity in the crystal volume.

Optical characterization and crystal structure of the novel bronzetype CaxBa1‐xNb2O6 (x = 0.28; CBN‐28)

“…Results and discussion Figure 1 shows a polished (001)-plate of Czochralski grown CBN-28 in normal illumination (figure 1a) and between crossed polarizers (figure 1b). Between crossed polarizers the (001)-plate offers a typical "core" or "ghost" structure with a highly disturbed crystal center and stress birefringence in the outer regions [7,8]. In the hk0-plate (figure 2) the stress birefringence is not visible.…”

Conical light scattering in strontium barium niobate crystals related to an intrinsic composition inhomogeneity

“…The relation of the scattering to the growth-induced seeding rod strongly points to the relation of the scattering cones to a composition inhomogeneity of the SBN crystal on the micro-scale. In [17] the origin of the core was analysed by physical-chemical methods. It was found that the rod originates from hydrodynamic conditions in the melt during crystal growth, together with the defect structure of the seed crystal.…”

Optical defects in barium—strontium niobate single crystals

“…Their review in (IVLEVA, KURMJNOV) was recently given. Growth striae with refraction index changed inside of them (DUDNIK et al 1972;DUDNIK et al 1975;BONIORT et al ;DUBOVIK et al), dislocations of different types (ITo, FURUHATA; ITO et al 1975; and "growth column" located in the centre of single crystal were observed in BSN crystals (ITO et al 1975;FTJRUHATA 1976;ABRAMOV et al). A method of growing of the crystals with dislocation density less than 10 cm-a was proposed ( ITO et al 1975;MACIOLEE et al).…”

“…Considerable stresses arising near the boundary of "growth column" make such crystals almost useless for electrooptic element production. The "growth column" is assumed not to be connected to "face effect" and be determined by hydrodynamic conditions in the melt under permanent rate crystal rotation in a steady crucible and perhaps defect structure of the seeding crystal ( ITO et al 1975 ;ABRAMOV et al).…”