Oxide Self-Flux in Optical Floating Zone Crystal Growth of Nickel Niobate (NiNb₂O₆)

Abstract

Growing crystals of nickel niobate (NiNb 2 O 6 ), we noticed that changing growth 1 conditions allowed our material to enter different areas of the phase diagram. We also found that 2 excess material accumulated within and above the liquid zone. Analysis showed that this was an 3 excess of NiO. Changing the ratio of the constituent oxides -an excess of ∼4% of either NiO or 4 Nb 2 O 5 gave us the opportunity to investigate changes in zone stability, melting temperature and 5 quality of the resulting crystal. We found that a small excess of nickel oxide decreases the melting 6 temperature significantly, and created the best pseudo-rutile NiNb 2 O 6 crystal studied (Pbcn, space 7 group 60), while higher amounts of niobium oxide allowed us to stabilize the NiNb 2 O 6 columbite 8 phase (P4 2 /n, space group 80). This research reinforces the idea that self-flux as a travelling solvent 9 can significantly impact crystal growth parameters and quality.