Phase Equilibria in the Quasi-Ternary System Cu2Se-In2Se3-CuI and the Crystal Structure of the AIBIII2XVI3YVII Compounds, Where AI-Cu, Ag; BIII-Ga; XVI-Cl, Br, I; YVII-S, Se, Te
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-12-01 |
| Journal | Journal of Phase Equilibria and Diffusion |
| Authors | І. А. Іващенко, В. С. Козак, L. D. Gulay, V. V. Galyan |
| Institutions | Cracow University of Technology, Lesya Ukrainka Volyn National University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study provides critical phase equilibrium and structural data for the Cu2Se-In2Se3-CuI quasi-ternary system, focusing on materials relevant to defective diamond-like semiconductors (DLS).
- Phase Mapping: The isothermal section at 770 K (497 °C) and the liquidus surface projection of the Cu2Se-In2Se3-CuI system were successfully constructed using XRD and DTA, defining primary crystallization regions.
- Quaternary Compound Stability: The key quaternary compound, CuIn2Se3I, was confirmed to melt congruently at 1213 K (940 °C), indicating high thermal stability suitable for crystal growth.
- Homogeneity Range: CuIn2Se3I exhibits significant solid solution regions, spanning 15 mol.% and 9 mol.% CuI within the composition triangle.
- Invariant Equilibria: Coordinates and types (eutectic and transition reactions) of 19 monovariant curves and 19 nonvariant points were established, providing a complete Scheil reaction scheme.
- Novel Structures Solved: The crystal structures of two new Ga-based chalcohalides, CuGa2Te3I and AgGa2Te3Br, were solved for the first time using the powder method.
- Structural Classification: Both new compounds crystallize in the tetragonal symmetry (Space Group I-4) and are confirmed as cation-deficient compounds with a 3:4 cation-to-anion ratio, linking them to known DLS structures (e.g., CdAl2S4 type).
Technical Specifications
Section titled “Technical Specifications”Key structural and thermal data extracted from the investigation of the Cu2Se-In2Se3-CuI system and related chalcohalides.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Isothermal Section Temperature | 770 (497) | K (°C) | Equilibrium study temperature. |
| CuIn2Se3I Melting Point | 1213 (940) | K (°C) | Congruent melting temperature. |
| CuIn2Se3I Homogeneity Region | 15 and 9 | mol.% CuI | Extent of solid solution within the triangle. |
| CuGa2Te3I Crystal System | Tetragonal | SG | Space Group I-4. |
| CuGa2Te3I Lattice Parameter (a) | 5.9147(4) | Angstrom | Unit cell dimension. |
| CuGa2Te3I Lattice Parameter (c) | 11.952(2) | Angstrom | Unit cell dimension. |
| AgGa2Te3Br Lattice Parameter (a) | 6.2977(3) | Angstrom | Unit cell dimension. |
| AgGa2Te3Br Lattice Parameter (c) | 11.9473(7) | Angstrom | Unit cell dimension. |
| Cation:Anion Ratio (AIBIII2XVI3YVII) | 3:4 | Ratio | Characteristic of defective diamond-like structure. |
| Nonvariant Transition Reaction (LU1) | 1185 | K | L + Cu3InSe3 ↔ ζ + α. |
| Nonvariant Eutectic Reaction (LE1) | 978 | K | L ↔ ε + η + ζ. |
Key Methodologies
Section titled “Key Methodologies”The synthesis and characterization of the alloys were performed using high-purity elements and controlled thermal processing in sealed ampoules.
- Precursor Synthesis: High-purity elements (Cu-99.99, In-99.99, Se-99.997 wt.%) were used. Cuprous iodide (CuI) was prepared chemically by reacting CuSO4·5H2O with NaI in the presence of SO2.
- Encapsulation: Prepared stoichiometric weights were sealed in evacuated ampoules (residual pressure 1.33 x 10-2 Pa) using a gas-oxygen burner and placed in protective metal tubes.
- Controlled Synthesis Cycle (Thermodent Furnace):
- Initial Heating: Ramped to 670 K at 10 K/h, followed by a 48 h anneal.
- Maximum Temperature: Heated to 1070 K, held for 48 h.
- Cooling: Cooled to 770 K at a rate of 20 K/h.
- Homogenization: Samples were subjected to a 300 h homogenizing anneal at 770 K to ensure the establishment of the equilibrium state.
- Phase Analysis (DTA): Differential Thermal Analysis (DTA) was conducted using a Thermodent H307/1 furnace with a Pt/Pt-Rh thermocouple to determine liquidus temperatures and invariant points.
- Structural Analysis (XRD): X-ray Diffraction (XRD) was performed on a DRON 4-13 diffractometer (CuKα radiation) for phase identification and construction of the isothermal section.
- Crystal Structure Determination: The structures of CuGa2Te3I and AgGa2Te3Br were refined using the powder method (Rietveld refinement) to determine atomic coordinates and unit cell parameters.
Commercial Applications
Section titled “Commercial Applications”The investigated chalcohalide compounds belong to the class of defective diamond-like semiconductors (DLS), which are highly valued in advanced electronic and optoelectronic applications due to their unique structural and electronic properties.
- Advanced Semiconductor Devices: Used in multiphase compositions for complex semiconductor devices where precise control over phase boundaries and solid solution regions is critical for performance.
- Photovoltaics (Solar Energy): DLS materials, including those based on Cu-In-Se systems (like CuInSe2), are foundational components in thin-film solar cells (CIGS technology). The halide inclusion (I, Br) can tune band gaps and stability.
- Thermoelectric Generators: Compounds with complex crystal structures and defects (like the cation-deficient structures found here) often exhibit low thermal conductivity, making them excellent candidates for converting waste heat into electrical energy.
- Optoelectronics and Sensors: The tetrahedral coordination and diamond-like structure are favorable for nonlinear optical applications and high-performance radiation detection.
- Materials Synthesis Engineering: The established phase diagrams (liquidus surface and isothermal sections) are essential for engineers developing reliable methods for growing high-quality single crystals of CuIn2Se3I and related solid solutions for commercial production.
View Original Abstract
Abstract The quasi-ternary system Cu 2 Se-In 2 Se 3 -CuI has been investigated by x-ray diffraction and differential thermal analysis. The isothermal section at 770 K and the liquidus surface projection of the system have been built. For the first time, the primary crystallization regions, and the coordinates of the invariant and monovariant equilibria have been determined. In the system, the regions of the solid solutions based on the binary, ternary, and quaternary compounds have been investigated. The formation of the CuIn 2 Se 3 I quaternary compound, which melts congruently at 1213 K and has a homogeneity region of 15 and 9 mol.% CuI within the composition triangle has been established. For the first time, the crystal structures of CuGa 2 Te 3 I and AgGa 2 Te 3 Br compounds have been studied using a powder method. They crystallize in the tetragonal symmetry, Space Group I -4, a = 5.9147(4) Å, c = 11.952(2) Å for CuGa 2 Te 3 I; a = 6.2977(3) Å, c = 11.9473(7) Å for AgGa 2 Te 3 Br compound, respectively. The connection of their structures with the structures of the defective diamond-like semiconductors has been discussed .