New Thallium Tellurides with Rare Earth Elements
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-12-15 |
| Journal | Конденсированные среды и межфазные границы |
| Authors | S. Z. Imamaliyeva |
| Institutions | Azerbaijan National Academy of Sciences |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: New Thallium Tellurides for Thermoelectrics
Section titled “Technical Documentation & Analysis: New Thallium Tellurides for Thermoelectrics”Executive Summary
Section titled “Executive Summary”This documentation analyzes the synthesis and characterization of new ternary thallium telluride compounds ($Tl_4LnTe_3$), focusing on their potential application in advanced functional materials, specifically thermoelectrics and magnetics.
- Core Achievement: Successful synthesis and structural indexing of five new $Tl_4LnTe_3$ compounds (Ln = Nd, Sm, Tb, Er, Tm), structural analogues of $Tl_5Te_3$.
- Structure & Method: Compounds crystallize in a tetragonal lattice (Space Group $I4/mcm$), synthesized via a high-temperature ceramic method involving fusion (1000 K) and prolonged annealing (700 K for 1000 h).
- Key Finding: A clear correlation was established between the crystal lattice parameters ($a$ and $c$) and the atomic number of the lanthanide, attributed to lanthanide contraction.
- Application Potential: The synthesized materials are identified as promising candidates for next-generation thermoelectric and magnetic devices.
- 6CCVD Relevance: The integration of these novel chalcogenides into functional devices requires substrates with extreme thermal management capabilities and chemical inertness, areas where 6CCVD’s MPCVD diamond excels.
- Value Proposition: 6CCVD offers custom Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) wafers, essential for high-efficiency thermoelectric device architectures requiring superior heat dissipation.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the research paper detailing the synthesis and structural properties of the $Tl_4LnTe_3$ compounds.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Crystal Structure | Tetragonal ($I4/mcm$) | N/A | Structural analogue of $Tl_5Te_3$ |
| Synthesis Method | Ceramic Method | N/A | Direct interaction in evacuated quartz ampoules |
| Initial Fusion Temperature | 1000 | K | Required for initial alloy formation |
| Annealing Temperature | 700 | K | Prolonged homogenization (1000 h) |
| Synthesis Pressure | 10-2 | Pa | Required vacuum level |
| Melting Point Range | 760 - 775 | K | Compounds melt with decomposition (peritectic reaction) |
| Smallest Lattice $a$ ($Tl_4TmTe_3$) | 8.8354(7) | Å | Correlates with lanthanide contraction |
| Largest Lattice $c$ ($Tl_4NdTe_3$) | 13.0952(12) | Å | Correlates with substitution of Tl(2) atoms by REE |
| Lanthanide Elements (Ln) | Nd, Sm, Tb, Er, Tm | N/A | Elements substituted into the $Tl_5Te_3$ structure |
Key Methodologies
Section titled “Key Methodologies”The $Tl_4LnTe_3$ compounds were synthesized using a specialized ceramic method to overcome the incongruent melting nature and refractoriness of the Rare Earth Elements (REE).
- Material Preparation: High-purity Tl, Te, and REE elements were used. Thallium was dried immediately before use due to its high reactivity with air.
- Stoichiometric Mixing: Stoichiometric amounts of $Tl_2Te$, Lanthanide, and elemental Te were used (rather than elementary components) to prevent the formation of stable Tl-Ln compounds.
- Encapsulation: Synthesis was performed in quartz ampoules evacuated to 10-2 Pa. To prevent interaction between lanthanides and the quartz walls, the ampoules were graphitized via thermal decomposition of toluene.
- Fusion: The mixture was fused at 1000 K.
- Homogenization: The resulting cast, non-homogenized ingots were ground into powder, pressed into cylindrical tablets, and subjected to prolonged annealing at 700 K for 1000 hours.
- Characterization: Single-phase confirmation was achieved using Differential Thermal Analysis (DTA) and X-ray Phase Diffraction (XRD). Lattice parameters were determined using the Le Bail refinement method (Topas 4.2 software).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The research highlights the development of novel thermoelectric and magnetic materials. Integrating these advanced chalcogenides into high-performance devices necessitates substrates capable of handling extreme thermal loads and providing stable interfaces—a core competency of 6CCVD’s MPCVD diamond.
Applicable Materials for Thermoelectric Integration
Section titled “Applicable Materials for Thermoelectric Integration”| 6CCVD Material | Specification | Relevance to $Tl_4LnTe_3$ Research |
|---|---|---|
| Thermal Grade PCD | Wafers up to 125mm. Thickness 0.1µm - 500µm. | Ideal for large-area thermoelectric modules requiring maximum heat spreading and mechanical robustness. Diamond’s thermal conductivity (> 2000 W/mK) is crucial for managing heat flux in high-efficiency devices. |
| High Purity SCD | Thickness 0.1µm - 500µm. Polishing Ra < 1nm. | Essential for fundamental studies, quantum computing applications (AMSQC funding context), or when ultra-low defect density and optical transparency are required for characterization. |
| Boron-Doped Diamond (BDD) | Custom doping levels (p-type semiconductor). | Can serve as an active electrode or integrated sensor layer, leveraging BDD’s stability and tunable conductivity in conjunction with the novel $Tl_4LnTe_3$ thermoelectric material. |
Customization Potential for Device Fabrication
Section titled “Customization Potential for Device Fabrication”To move these novel materials from synthesis to functional devices, precise integration and interfacing are required. 6CCVD offers comprehensive customization services that directly support this transition:
- Custom Dimensions: While the paper focuses on bulk synthesis, device prototyping requires specific geometries. 6CCVD provides custom plates and wafers up to 125mm (PCD) and substrates up to 10mm thick, tailored to specific device footprints.
- High-Precision Polishing: Achieving intimate contact between the $Tl_4LnTe_3$ layer and the substrate is critical for thermal and electrical performance. 6CCVD guarantees ultra-smooth surfaces: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD.
- Integrated Metalization: For creating robust electrical contacts (e.g., for Hall measurements or device interconnects), 6CCVD offers in-house metalization services, including:
- Standard Stacks: Ti/Pt/Au, Ti/W/Cu.
- Custom Stacks: Utilizing Au, Pt, Pd, Ti, W, Cu, tailored to the specific chemical requirements of the telluride interface.
Engineering Support
Section titled “Engineering Support”The synthesis of complex ternary chalcogenides like $Tl_4LnTe_3$ requires specialized knowledge in material compatibility and thermal management.
- Expert Consultation: 6CCVD’s in-house PhD team specializes in diamond material science and advanced device integration. We can assist researchers in selecting the optimal diamond grade (SCD vs. PCD) and thickness for similar Thermoelectric and Magnetic Material projects.
- Global Supply Chain: We ensure reliable, global delivery of custom diamond solutions (DDU default, DDP available) to support international research collaborations, such as those mentioned in the paper (Azerbaijan/Spain).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Compounds of the Tl4LnTe3 (Ln-Nd, Sm, Tb, Er, Tm) composition were synthesized by the direct interaction of stoichiometric amounts of thallium telluride Tl2Te elementary rare earth elements (REE) and tellurium in evacuated (10-2 Pa) quartz ampoules. The samples obtained were identified by differential thermal and X-ray phase analyses. Based on the data from the heating thermograms, it was shown that these compounds melt with decomposition by peritectic reactions. Analysis of powder diffraction patterns showed that they were completely indexed in a tetragonal lattice of the Tl5Te3 type (space group I4/mcm). Using the Le Bail refinement, the crystal lattice parameters of the synthesized compounds were calculated.It was found that when the thallium atoms located in the centres of the octahedra were substituted by REE atoms, there occurred a sharp decrease in the а parameter and an increase in the с parameter. This was due to the fact that the substitution of thallium atoms with REE cations led to the strengthening of chemical bonds with tellurium atoms. This was accompanied by some distortion of octahedra and an increase in the с parameter. A correlation between the parameters of the crystal lattices and the atomic number of the lanthanide was revealed: during the transition from neodymium to thulium, therewas an almost linear decrease in both parameters of the crystal lattice, which was apparently associated with lanthanide contraction. The obtained new compounds complement the extensive class of ternary compounds - structural analogues of Tl5Te3 and are of interest as potential thermoelectric and magnetic materials.
 
 
 
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