Room‐Temperature Sol–Gel Synthesis of Sodium Hexaniobate in an Immiscible Hexane–Water System and Its Conversion into NaNbO₃

Abstract

Sodium hexaniobate (Na 7 [HNb 6 O 19 ]·15H 2 O) was synthesized by a one-pot sol-gel method at room temperature by using an immiscible, biphasic solution. An organic solution was prepared by dissolving niobium pentaethoxide [Nb(OC 2 H 5 ) 5 ] in ethanol, which was then added to hexane. This solution was brought into contact with an aqueous NaOH solution to form a reaction system consisting of two separate phases. A white precipitate was formed within 12 h at the bottom of the aqueous solution. It exhibited well-defined rod-like morphology on a micrometer scale. A compar-

Rod-like NaNbO3: mechanisms for stable solvothermal synthesis, temperature-mediated phase transitions and morphological evolution

“…35 Conventionally, synthesizing the same products via hydrothermal route requires a higher alkalinity ranging from 10 M to 15 M, and the formation process is difficult to control. [36][37][38] The IPA-based solvothermal strategy provides a facile, controllable, and moderate process for obtaining intermediate Na In a previous study, alkaline niobate powders were synthesized in solution via a dissolution-precipitation process, 39 and the pertinent reaction processes can be written as follows: 40…”

A biphasic sol–gel route to synthesize anatase TiO2particles under controlled conditions and their DSSC application

“…The promotion is explained by the decreased pH values (the increased [H + ]). It was argued that the hydrolysis of TTIP with affluent water could generate soluble Ti(OH) 4 and Ti(OH) 3 + species under the neutral and the acidic condition, respectively [12][13][14]. The Ti(OH) 3 + species is thermodynamically more close to anatase and actually crystallized more easily than the Ti(OH) 4 species [12].…”

“…Recently, we have developed a biphasic sol-gel method to reduce the hydrolysis reaction rate of metal alkoxides and synthesize metal oxide materials in a more controlled manner [4][5][6]. In this method, metal alkoxides are dissolved in organic solvents, which are subsequently contacted with water or aqueous solutions.…”

“…If the organic solvents used are immiscible with water, they can form biphasic liquid systems where the hydrolysis reaction is limited to either of the liquid phases or their interface. Our approach was to synthesize morphology-controlled complex metal oxides such as NaNbO 3 [4], CaNb 2 O 6 [5], or Ba 2 V 2 O 7 [6] and, if possible, to improve their physical properties. Actually a luminescence property of the thus synthesized niobate and vanadate was found to be superior to those obtained by a usual sol-gel method with a single-phase liquid system.…”

Synthesis of blue-luminescent CaNb₂O₆ by using a biphasic liquid method at low temperatures

“…In this article, we propose a new synthesis of CaNb 2 O 6 through a biphasic liquid method. 16 O] was dissolved in water. The resultant solutions were immiscible and then biphasically separated after putting them together.…”