Growth and characterization of RM3(BO3)4 crystals

Crystal growth and X-ray topography of NdAl3(BO3)4

The solubility of NdAl3(BO3)4 crystals in a 69.4 wt% K2Mo3O10−18.1 wt% Nd2O3−12.5 wt% B2O3 multicomponent flux has been investigated. Their growth kinetics was determined in the temperature range of 1050–1000 °C and growth rates were found to be within 0.05–0.14 μm min−1 depending on fluxed melt supercooling (supersaturation). With increased supercooling up to 15 °C, the growth rate rises linearly, but then reaches a temperature plateau and decreases slowly because of spontaneous nucleation in the fluxed melt volume at a comparatively higher supercooling. The growth rate data were analyzed according to a simple diffusion model. NdAl3(BO3)4 single crystals (7 × 10 × 20 mm) have been obtained by high-temperature solution growth on dipped seeds.

Flux growth of NdAl3(BO3)4 single crystals from a K2Mo3O10 based system

Crystal growth of NdAl3(BO3)4 from K2O/MoO3/Nd2O3/B2O3/KF flux

Yb:YAl3(BO3)4 is a good self-frequency-doubling crystal with the point group 32. In this paper, atomic force microscopy (AFM) has been used to observe the etch figures of the three forms (positive trigonal prism {11\overline 20}, negative trigonal prism {2\overline 1\overline 10} and rhombohedron {10\overline 11}) on the crystal morphology of Yb:YAl3(BO3)4. The etch figures display the point group 32 of the Yb:YAl3(BO3)4 crystal. To compare the morphology and etch figures of Yb:YAl3(BO3)4 with those of quartz, the classic crystal of point group 32, the etch figures of the three forms (hexagonal prism {10\overline 10}, positive rhombohedron {10\overline 11} and negative rhombohedron {01\overline 11}) on quartz were also observed using AFM. It is interesting that Yb:YAl3(BO3)4 develops two prismatic forms (related by a positive–negative relationship) and one rhombohedral form, while quartz develops one prismatic form and two rhombohedral forms (also related by a positive–negative relationship). Etch figures of faces or sections with the same indices (or the same crystallographic orientations) in Yb:YAl3(BO3)4 and quartz are very similar, although their crystal structures are very different. Besides diffraction methods, etch figures are a useful method for determining the point group of a crystal.

G. Bocelli

Papers

Growth, morphological and structural investigations of neodymium aluminium borate crystals from different flux systems