Optical Observation of Striations in Y2Ti2O7 Single Crystals

Abstract

RE2Ti2O7 (RE = Y, Yb, Ho, Er) pyrochlores are very interesting as potential candidates for host materials for applications in transition-metal ions lasers. Y2Ti2O7 crystals were grown by the optical floating zone (OFZ) method. The shape of the growth interface is of paramount importance for the growth of single crystals. As striation and the growth interface have the same shape, we observed the striations in as-grown crystals under polarized light. The degree of overheating of the molten zone influences the shape of the growth interface. An increase of power supplied to the molten zone combined with a decrease of both, thermal conductivity and the amount of heat dissipated by the seed-rod, causes an increase in the degree of overheating of the floating zone. Under a high degree of overheating, the interface of the crystal grown is less convex, with smaller curvature. With the speed of rotation of these crystals decreasing from 30 to 7 rpm, the curvature of striations decreases and the shape of the growth interface changes from convex to less convex, and finally to concave.

High oxygen pressure floating zone growth and crystal structure of the metallic nickelates R4Ni3O10 ( R=La,<

“…As demonstrated in Ref. [43] for floating zone growth of Y2Ti2O7, the shape of the growth interface changes from convex to less convex, and finally to concave with the speed of rotation of the crystals decreasing from 30 to 7 rpm. In our crystal growth, we applied rotation speeds of 27 and 20 rpm for feeding rod and seed, respectively, to achieve a stable melt zone and a convex growth front.…”

Structural, optical and mechanical properties of Y2Ti2O7 single crystal

“…The important factor to grow good quality single crystal by OFZ is to achieve a stable molten zone by controlling the shape of the solid -liquid (S-L) interface. The shape of S-L interface depends on growth parameters such as the lamp power, the speed of seed / feed rotation, growth rate and the applied ambient gas composition and pressure [18][19][20]. A large deviation from the optimized growth parameters leads to striation, crack and local lattice deformations in the grown crystals.…”

“…The single crystals of pyrochlore oxides are generally grown by Czochralski method, flux growth technique and optical floating zone (OFZ) technique [18][19][20]. Of them, OFZ method has advantages over other growth methods since it is a crucible-free technique.…”