Synthesis And Morphology Characterization Of Indium Oxide (In₂O₃) Crystals

In this paper, In(OH)3, InOOH and In2O3 crystals were synthesized by hydrothermal method with pure water or 1 mol/L KOH,5 mol/L KOH as mineralizer, and In(OH)3 as the precursor. The fill factor is 35%, and the reaction time is 24 h. The rules of phase transformation of In(OH)3, InOOH and In2O3 were explored at different temperatures of 200℃,250℃and 350℃. and their morphologies were analyzed.It is found that the phase transformation and obvious secondary crystallization of In(OH)3 did not occurred on the condition of pure water at 200℃. The crystals didn't have specific morphology. And the crystals transformed to InOOH at the temperature of 250℃and 350℃.When 1 mol/L KOH and 5 mol/L KOH was used as mineralizer at the reaction temperature of 200℃, the crystals turned up secondary crystallization. Especially when using 5 mol/L KOH as mineralizer, the largest crystals scale reached to 20μm and the smallest was less than 100 nm, displaying the process of multiple-crystallization. When the temperature was up to 250℃, InOOH and a few In2O3 crystals were synthesized. When above 350℃, cubic bixbyite-type phase In2O3 were synthesized. The side length of the crystal exceeded 50μm, exposing{001},{010},{100} and{101} facets.The two phases of marketable-In2O3 crystalls, cubic bixbyite-type struture and corundum-type structure, converted into cubic bixbyite-type In2O3 crystalls with 3 mol/L KOH as mineralizer. The fill factor is 35%, and the reaction temperature is 430℃. It is indicated cubic bixbyite-type phase was more stable than corundum-type phase on the condition of hydro-thermal synthesis.The cubic bixbyite-type In2O3 crystalls were also synthesized with mineralizer of 10 mol/L KOH, the fill factor of 35%, reaction temperature of 430℃, and with precursor In2O3 and 10% mol ratio FeSO4·7H2O by hydro-thermal method. The morphology had been obviously changed by doping with Fe into In2O3. The crystalls exposed high index crystal {101} facets. Part of synthetic products were ferromagnetic Fe3O4 spinel, exposing {111} facets.The cubic bixbyite-type In2O3 crystalls were also synthesized by chemistry vapour method. They appeared octahedron shape, exposing {111} facets. The maximum length of edge was 50μm.