Dislocations in Strontium Barium Niobate

Abstract

The distribution of dislocations in strontium barium niobate (SBN) crystals is examined by etching and by optical microscopy, and the sources of the dislocations are also investigated. The dislocations can be put into three categories according to the characteristics of distribution patterns. The dislocations concentrated in the central region of the crystal originate from the dislocations and the residual surface damages in the seed. The dislocations aligned radially in the outer region of the crystal are generated by the lattice mismatching or thermal stress at the groove bottoms in the shoulder part of the crystal. Finally, the dislocations distributed randomly in the outer region are generated at the positions where Pt or SBN were adsorbed on the surface of the crystal body. Methods for eliminating the dislocations are also described.

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

“…In the second case, the inhomogeneity is marked by stripes parallel to the c axis (see figure 7(a)), which corresponds to the ring-shaped area in figure 7(b). This inhomogeneity can be assigned to the growth-induced seeding rod reported in [16].…”

Optical defects in barium—strontium niobate single crystals

“…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). The purpose of this paper is to clear out the nature of "growth column", to investigate residual stresses and methods of eliminating growth striae in crystals.…”

“…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).…”