Synthesis and Reaction Mechanism of Cu2ZnSnS4 Powders

Autor: Cheng-Fu Huang, 黃丞甫
Rok vydání: 2012
Druh dokumentu: 學位論文 ; thesis
Popis: 100
Cu2ZnSnS4 (CZTS) powders have been synthesized from aqueous solutions consisting of copper (II) chloride, zinc (II) chloride, stannic (IV) chloride, and thioacetamide (TAA) dissolved in mixtures of deionized water and ethanol. The CZTS powders were obtained when the precursor solutions were held isothermally at 65 oC followed by annealing at 550 oC in Ar atmosphere. When the reaction temperature was held at 35 to 55 oC, a pronounced formation of intermediate Cu3(TAA)3Cl3 prisms resulted which produced Cu2S at elevated temperatures as an impurity. In addition, rounded particles were obtained from the CZTS precursor solutions by filtering removal of the Cu3(TAA)3Cl3 prisms. Since Zn was present as Zn2+ ions in the reaction solution, Cu2SnS3 (CTS) resulted rather than the formation of CZTS when the rounded particles were annealed at 450 ¬oC. Therefore, a successful synthesis of the CZTS powders requires annealing of the solution containing Zn2+ and the precipitate in the same pot. From thermal analyses, crystalline CZTS powders began to form as the annealing temperature was raised above 210 oC. XRD pattern revealed that the CZTS diffraction peaks appeared when the annealing temperature was raised to 250 oC and no other phases were observed. We have also conducted separate experiments involving CuCl2, ZnCl2, SnCl4, CuCl2+ZnCl2, CuCl2+SnCl4 mixture with the TAA respectively and reacted isothermally at 65 oC for 1 h. After the reaction, the solutions were annealed at 190 oC and 250 oC, respectively. When the annealing temperature was increased, following reaction steps resulted: (1) Cu2+ ions were firstly reduced to Cu+ which facilitated Cu2S formation；(2) (NH4)2ZnCl4 → ZnS；(3) (NH4)2SnCl6 → SnS2. The Cu2S reacted with SnS2 to form CTS first, and then CTS reacted with ZnS to form the CZTS powders.
Databáze: Networked Digital Library of Theses & Dissertations
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