One-Dimensional Growth of Li₂NiPO₄F Single Crystals from Intermediate LiNiPO₄ Crystal Surface Using KCl–KI Fluxes

Abstract

The shape of an inorganic material affects its luminescence, catalytic activity, surface energy, solubility, and conductivity, which are important properties of a functional inorganic material. Herein, we demonstrate the one-dimensional growth of Li2NiPO4F single crystals from a KCl–KI binary flux; these crystals are oriented along the b axis through the conversion of intermediate LiNiPO4. The crystal surface was assigned as {h0l} and included {100} and {001} as major faces. The formation mechanism and growth manner are discussed in terms of phase transitions and morphological changes. Since the LiNiPO4 surface was gradually converted into Li2NiPO4F by reacting with LiF, as evidenced from cross-sectional scanning electron microscopy observations, we speculate that the growth of one-dimensional crystals toward the exterior of LiNiPO4 was driven by the relaxation of compressive stresses formed on the surface as well as by the formation of a steep supersaturation gradient near the LiNiPO4 surface.

Platy BaTaO2N Crystals Fabricated from K2CO3–KCl Binary Flux for Photocatalytic H2 Evolution

“…A few studies noted that the combination of two kinds of flux (binary flux) with different properties can tailor the crystal morphology, which has inspired us to employ a suitable binary flux in the nitridation process to control the particulate structure of the BaTaO 2 N crystals. − In the current study, we focus on the fabrication of platy BaTaO 2 N crystals with a lower defect density and higher crystallinity by simply varying the molar ratio of K 2 CO 3 /KCl during the nitridation process. Subsequently, the formation mechanisms of the platy BaTaO 2 N crystals and the effects of the K 2 CO 3 /KCl molar ratio on the photocatalytic activity for H 2 evolution were investigated.…”

“Soft” Alkali Bromide and Iodide Fluxes for Crystal Growth

“…The ABI fluxes have also been used to control the crystal morphology of several oxides such as NaNd(MoO 4 ) 2 (Liu et al, 2016 ), KEu(MoO 4 ) 2 (Wu et al, 2013 ), Li 2 NiPO 4 F (Yamada et al, 2018 ), and NaNbO 3 (Hamilton et al, 2020 ). In each case the identity of the flux or the amount of flux played a significant role in the crystal morphology.…”

“…Crystals of Li 2 NiPO 4 F were grown from mixtures of LiCO 3 , NiO, NH 4 H 2 PO 4 that were preheated at 400°C for 3 h before adding LiF and excess KCl/KI flux and heating the mixture to 600°C for 1 h. The morphology of the Li 2 NiPO 4 F crystals was sensitive to the ratio of the preheated reactants and to the amount of KCl/KI flux ( Figure 4 ). By increasing the amount of the flux, the morphology of the crystals changed from undefined to faceted, to rectangularly shaped, to one dimensional rods (Yamada et al, 2018 ).…”

“…(F) Lower magnification image of (E) . Reproduced from Yamada et al ( 2018 ) with permission of American Chemical Society.…”

Exclusive Growth of Low-Aspect Ratio, Polyhedral h-BN Crystals in Molten Li2CO3 as the Reactive Flux

“…With this method, the growth forms can be controlled. In fact, we have grown several crystals − to potentially improve the performance of a material, such as electronic/ionic conduction and energy conversion, based on the superior crystallographic features in terms of crystallinity and crystal facets. , Although our attempts to change the morphology was successful, controlling the same still remains a challenge because the crystal growth in the flux method mainly relies on crystallization from supersaturation. This is strongly dependent on the surface energy even in the nonequilibrium shape, which is why there are only limited crystal habits for h-BN crystals.…”