Structure Deformation in GdCOB Single Crystals Grown by the Czochralski Method

Abstract

Gadolinium calcium oxide borate GdCa4O(BO3)3 melts congruently, and single crystals with diameters of up to 35 mm and lengths of up to 70 mm were grown by the Czochralski method. Deformation of the crystal structure was observed. X-ray topography and conoscopic and polariscopic investigations revealed the core situated in the central part of the crystal, which was not visible with the naked eye. The relative (b/b av) difference in the lattice parameter b in the core region compared with the neighboring crystal areas was evaluated to be on the order of 9.6 × 10−4. Outside of the core region the mean value of the lattice parameter is constant, while fluctuations in spatial distribution of the Bragg angle were discovered. The effect of growth instabilities causes a certain deformation of the growth plane (interface). However, it did not disturb optical properties, and was quite a good crystalline area to yield a considerable second harmonic (532 nm) power in laser experiments.

Nature and spatial distribution of extended defects in Czochralski-grown Ca3RE2(BO3)4(RE = Y, Gd) orthoborate single crystals

“…Single crystal diffraction experiments at room and high temperatures have been done for Sr 3 Gd 2 (BO 3 ) 4 -the possible presence of twin and monoclinic crystal phase (instead of assumed orthorhombic one) at room temperature and so-called higher-order phase transition at ~700 °C have been observed [34,35]. Single-crystal defect structure has been also analyzed for Ca 4 GdO(BO 3 ) 3 by transmission and back-reflection x-ray topography [36], optical conoscopy, and spectropolarimetry [37]. Another single crystal from the same family-Er and Yb co-doped Ca 4 YO(BO 3 ) 3 -has been characterized by means of x-ray synchrotron transmission topography [38,39] and chemical etching [39].…”

Bulk growth and nonlinear optical properties of thulium calcium oxyborate single crystals

“…Rare-earth calcium oxyborate crystals ReCa 4 O(BO 3 ) 3 (ReCOB, Re: rare-earth elements) with monoclinic symmetry have been investigated for NLO applications in the last two decades. [20][21][22][23][24][25][26][27][28] Compared to the commercial LBO, BBO, KDP, DKDP, and KTP crystals, ReCOB crystals were reported to possess attractive NLO properties, such as low walk-off angles (about half of that of LBO for type-I phase matching), relatively larger d eff values (about four to five times those of KDP and DKDP), high damage threshold (comparable to that of LBO), and relatively large angular acceptance angles (approximately two times that of BBO). 18,19,[29][30][31] Of particular significance is that these crystals show highly stable mechanical and chemical properties and can be readily grown to have a large crystal size (4 inches) by using the Czochralski (Cz) method.…”