SEMICONDUCTOR, MOLECULAR CRYSTALS AND OXIDE TEMPERATURE PRESSURE OPHASE DIAGRAM
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-03-30 |
| Journal | International Journal of Heat and Technology |
| Authors | S. ZHANG, L. Chen |
| Institutions | Jilin Jianzhu University |
| Analysis | Full AI Review Included |
6CCVD Technical Documentation: Phase Diagram Prediction for Materials under Extreme Conditions
Section titled â6CCVD Technical Documentation: Phase Diagram Prediction for Materials under Extreme ConditionsâReference Paper: Semiconductor, Molecular Crystals and Oxide Temperature Pressure Ophage Diagram (Int. J. Heat Technology, 2015)
Executive Summary
Section titled âExecutive SummaryâThis paper presents a robust thermodynamic model utilizing the Clapeyron equation to accurately predict Temperature-Pressure (T-P) phase diagrams, offering critical insight into material stability under extreme environments.
- Core Achievement: Demonstrated high reliability of the T-P phase diagram model by successfully comparing predictions against experimental results for key semiconductors (Si, Ge) and refractory oxides (Al2O3, MgO).
- Methodology: The model successfully integrated the effect of surface stress ($f$) via the Laplace-Young equation to define pressure-dependent volume change ($\Delta V_{m}(P)$), allowing for accurate modeling of both bulk and nanocrystalline materials.
- Key Materials Validated: The research confirmed the stability fields and melting curves for materials critical to high-temperature and high-pressure industrial applications, including corundum (Al2O3) and magnesia (MgO).
- Application Relevance: The findings are directly applicable to optimizing high-pressure synthesis and measurement techniques, particularly those utilizing the Diamond Anvil Cell (DAC).
- Pressure Regime: Accurate modeling was achieved for materials experiencing pressures up to 25 GPa and temperatures up to 4000 K, validating the generalizability of the approach for first-order phase transitions.
- 6CCVD Connection: The reliance of this research area on the Diamond Anvil Cell technique underscores the necessity for high-purity, structurally robust Single Crystal Diamond (SCD) components, a core offering of 6CCVD.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard parameters, used or derived in the calculation of the T-P phase diagrams for bulk materials, highlight the extreme conditions analyzed.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Bulk Si Melting Temp (TmI) | 1693 | K | Diamond Structure (I) to Liquid (L) Transition |
| Bulk Ge Melting Temp (TmI) | 1210.4 | K | Diamond Structure (I) to Liquid (L) Transition |
| Si I-II Transition Pressure (PI-IId) | 12 | GPa | Transition from Diamond (I) to $\beta$-Sn Structure (II) |
| Ge I-II Transition Pressure (PI-IId) | 10 | GPa | Transition from Diamond (I) to $\beta$-Sn Structure (II) |
| Al2O3 Melting Temp (Tm) @ Ambient P | 2327 | K | Reference Melting Temperature |
| Al2O3 Calculated Nanocrystal Pressure (Pi) | 20.10 | GPa | Curvature-induced pressure for Dmin = 1.146 nm |
| MgO Calculated Nanocrystal Pressure (Pi) | 25.39 | GPa | Curvature-induced pressure for Dmin = 1.284 nm |
| MgO Melting Temp (Tm) @ 30 GPa | ~3900 | K | Predicted high-pressure melting point (Figure 5) |
| Al2O3 Bulk Modulus (B) | 289.55 | GPa | Required input for compressibility ($\kappa$) calculation |
| Al2O3 Surface Stress ($f$) | 4.5 | J · m-2 | Calculated using thermodynamic inputs |
Key Methodologies
Section titled âKey MethodologiesâThe study relied on a generalized thermodynamic approach, integrating empirical data with fundamental phase transition equations.
- Phase Transition Law Application: Utilized the classic Clapeyron equation to calculate the joint rate of change dP/dTm along the phase equilibrium lines governing first-order phase transitions.
- Thermodynamic Variable Modeling: Assumed functional dependencies for the changes in melting enthalpy ($\Delta H_{m}$) and volume ($\Delta V_{m}$).
- $\Delta H_{m}(T_{m})$ was modeled based on a linear approximation of heat capacity difference ($\Delta C_{p}$).
- $\Delta V_{m}(P)$ was modeled as pressure-dependent, incorporating compressibility data for both solid and liquid phases.
- Inclusion of Surface Stress Effects: Introduced a non-adjustable parameter, surface stress ($f$), established from a general equation based on melting entropy and bulk modulus. This allowed the modeling of the internal pressure ($P_{i}$) in nanocrystals via the Laplace-Young equation ($P_{i}$ = 4$f$/D).
- Integration of Pressure Sources: Generalized the pressure variable ($P$) to represent the sum of the external pressure ($P_{e}$) and the internal surface stress-induced pressure ($P_{i}$), enabling the model to predict both size-dependent and pressure-dependent melting behavior.
- Validation: The derived $T_{m}(P)$ curves were verified by comparison against existing experimental T-P diagrams, many of which were established using the Diamond Anvil Cell (DAC) technique.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research field detailedâpredicting material stability under extreme GPa pressures and thousands of Kelvin temperaturesâis fundamentally reliant on the performance of diamond, particularly in the Diamond Anvil Cell (DAC) technique mentioned in the Introduction. 6CCVD is an expert supplier of MPCVD diamond materials optimized for these environments.
| Research Requirement/Application | 6CCVD Material & Capability | Sales Advantage |
|---|---|---|
| High-Pressure Anvil Construction (DAC) | Single Crystal Diamond (SCD): Required for anvils due to its unmatched hardness, highest thermal conductivity, and chemical inertness. | We offer Optical Grade SCD plates and wafers up to 500”m thickness, guaranteed for maximum structural integrity under extreme compression. |
| In-Situ Optical Measurement | High Purity SCD Wafers: Essential for optical transmission windows to monitor phase transitions (e.g., Raman or luminescence spectroscopy) under pressure. | Polishing services guarantee Ra < 1nm for SCD, minimizing internal stress and scatter, vital for precise optical alignment in DAC research. |
| Synthesis/Substrate for Refractory Materials | Polycrystalline Diamond (PCD) Substrates: Stable platform for growing or testing materials like Al2O3 and MgO precursors under simulated deep-earth conditions. | PCD plates available up to 125mm diameter, offering researchers and engineers scalable synthesis platforms and heat spreading solutions. |
| High P/T Electrical Measurements | Boron-Doped Diamond (BDD): Used as stable, conductive electrode layers or heating elements within the high-pressure environment. | 6CCVD supplies Custom BDD materials, enabling precise resistive heating and electrical sensing where traditional metals fail. |
| Custom Electrode/Heating Element Creation | Custom Metalization and Etching: Internal capability to deposit thin films of Au, Pt, Pd, Ti, W, and Cu for electrodes or gaskets, often needed to interface with samples like Si or Ge in high-pressure cells. | Precise Laser Cutting Services ensure complex geometries and tight dimensional tolerances required for DAC assembly and advanced synthesis chambers. |
Engineering Support: 6CCVDâs in-house PhD team provides specialized consultation regarding material selection, purity grades, and dimensional customization necessary to replicate or extend high-pressure, high-temperature stability projects similar to the T-P phase diagram analysis presented in this paper.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The melting temperature-pressure phase diagram [Tm(P)-P] for semiconductor, molecular crystals and oxide are predicted through the Clapeyron equation where the pressure-dependent volume difference is modeled by introducing the effect of surface stress induced pressure.Semiconductor, molecular crystals and oxide have been employed to test the reliability of the model, because of its important role.For Si and Ge, the stable state under normal pressure is the diamond structure (Si-I and Ge-I).Through pressure, this change in the diamond structure for beta -Sn structure (Si-II and Ge-II), and with the increase of temperature, phase I and II are going to be melting into a liquid (L).For the CO2 crystal (commonly known as dry ice), it is a molecular solid with a structure of Pa3 at low temperature and low pressure (CO2-I), and can be widely used for cooling.Al2O3 has been extensively investigated because of its widely ranging industrial applications.This includes applications as a refractory material both of high hardness and stability up to high temperatures, as a support matrix in catalysis.MgO is a material of key importance to earth sciences and solid-state physics: it is one of the most abundant minerals in the Earth and a prototype material for a large group of ionic oxides.