Flux growth utilizing the reaction between flux and crucible

Abstract

Flux growth involves dissolving the components of the target compound in an appropriate flux at high temperatures and then crystallizing under supersaturation controlled by cooling or evaporating the flux. A refractory crucible is generally used to contain the high temperature melt. The reaction between the melt and crucible materials can modify the composition of the melt, which typically results in growth failure, or contaminates the crystals. Thus one principle in designing a flux growth is to select suitable flux and crucible materials thus to avoid any reaction between them. In this paper, we review two cases of flux growth in which the reaction between flux and Al2O3 crucible tunes the oxygen content in the melt and helps the crystallization of desired compositions. For the case of La5Pb3O, Al2O3 crucible oxidizes La to form a passivating La2O3 layer which not only prevents further oxidization of La in the melt but also provides [O] to the melt. For the case of La0.4Na0.6Fe2As2, it is believed that the Al2O3 crucible reacts with NaAsO2 and the reaction consumes oxygen in the melt thus maintaining an oxygen-free environment.

U8Al19Si6, A Uranium Aluminide Silicide with a Stuffed Supercell Grown from Aluminum Flux

“…Many examples of reaction of a metal flux with a crucible material have been reported. This can either be detrimental, leading to contamination of desired products, or adventitious, leading to unexpected new materials . Some recent examples of the latter are the leaching of iron out of steel crucibles, which produced an unusual nitridoferrate­(I) Ca 6 (Li x Fe 1– x )­Te 2 N 3 , and the partial reduction of alumina crucibles by a strongly reducing rare-earth based flux, which produced Nd 8 Co 4– x Al x Ge 2 C 3 . , However, this synthesis of U 8 Al 19 Si 6 is notable in that it appears that it is the surface composition of the alumina that is critical.…”

Growth of delafossite CuAlO2 single crystals in a reactive crucible

“…In summary, we have reported the growth of mm-sized CAO single crystals in a reactive alumina crucible. Unlike the conventional flux growth, in which the flux acts as a solvent to dissolve the desired substance, in the method reported in this paper, the flux also plays the role of the starting material that reacts with reactive crucible [20]. High-quality single crystals of CAO without the remaining flux were successfully obtained by the reaction between the Cu 2 O flux and alumina crucible.…”

Multicomponent flux growth and composition control of Cu2MnBO5:Ga ludwigites

“…Growing single crystals of different compounds and structures from multicomponent fluxes is quite a complicated but perspective problem: on the one hand, it provides a wide range of opportunities for varying the growth conditions; on the other hand, it introduces a significant uncertainty to the crystallizing phase sequence with the possible admixture of solvent components to the crystal content. [1][2][3] Using simple solvents with a composition much closer to the composition of the desired phase, including the ludwigite system, seems to be the easiest way to obtain the required crystals. [4][5][6][7] Unfortunately, this approach seldom allows obtaining single crystals of sufficient size, unlike the "risky" application of multicomponent solvents.…”