Experimental study of thermal conductivity at high pressures - Implications for the deep Earth’s interior
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2015-02-24 |
| Journal | Physics of The Earth and Planetary Interiors |
| Authors | Alexander F. Goncharov, Sergey S. Lobanov, Xiaojing Tan, Gregory T. Hohensee, David G. Cahill |
| Institutions | V.S. Sobolev Institute of Geology and Mineralogy, Institute of Solid State Physics |
| Citations | 46 |
| Analysis | Full AI Review Included |
Technical Analysis and Commercial Documentation: Thermal Transport in Deep Earth Minerals
Section titled “Technical Analysis and Commercial Documentation: Thermal Transport in Deep Earth Minerals”This documentation analyzes the techniques used in the study “Experimental study of thermal conductivity at high pressures: implications for the deep Earth’s interior.” The methodology, reliant on Time-Domain Thermoreflectance (TDTR) and high-pressure optical spectroscopy within Diamond Anvil Cells (DACs), directly correlates with 6CCVD’s specialized capabilities in custom MPCVD diamond materials, precision polishing, and thin-film metalization.
Executive Summary
Section titled “Executive Summary”This research utilizes advanced techniques in Single Crystal Diamond (SCD) platforms to investigate the thermal conductivity of lower mantle minerals (ferropericlase and bridgmanite) under extreme pressure (P) and temperature (T) conditions.
- Platform Dependency: The entire study is predicated on the use of high-quality, optically pure SCD anvils capable of supporting pressures up to 46 GPa while maintaining spectroscopic access.
- Techniques Employed: Lattice thermal conductivity ($\kappa$) was determined using Time-Domain Thermoreflectance (TDTR), requiring ultra-precise thin-film metalization (80 nm Al) on 15 µm thick SCD-polished samples.
- Radiative Conductivity ($\kappa_R$): Measured via optical spectroscopy, facilitated by a novel supercontinuum light source, demanding DAC optical windows with minimal chromatic aberration.
- Key Finding (Lattice $\kappa$): Ferropericlase ($\text{Mg}{0.9}\text{Fe}{0.1}\text{O}$) exhibits a significantly faster pressure dependency for lattice thermal conductivity (6.1(7)%/GPa) compared to pure MgO (3.6%/GPa).
- Key Finding (Radiative $\kappa_R$): Measurements confirm the reduced radiative conductivity scenario for the Earth’s lower mantle, largely pressure-independent up to 46 GPa.
- Future Requirements: The continuation of this research into high P-T regimes (above 1000 K) requires increasingly robust, high-performance SCD windows and conductive elements.
Technical Specifications
Section titled “Technical Specifications”The following parameters define the extreme conditions and precision required for the reported high-pressure thermal conductivity measurements.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Pressure Achieved | 46 | GPa | For radiative conductivity ($\kappa_R$) measurements (Bridgmanite) |
| Maximum Pressure (Lattice $\kappa$) | 30 | GPa | For lattice conductivity measurements (Ferropericlase) |
| Temperature Range (TDTR) | 300 | K | Room temperature measurement of lattice conductivity |
| Sample Thickness (Ferropericlase) | 15 | µm | Polished SCD thickness requirement |
| Surface Finish (Ferropericlase) | 0.3 | µm grit | Final polishing requirement |
| Transducer Metalization | 80 | nm | Aluminum (Al) film thickness applied via magnetron sputtering |
| TDTR Pump Pulse Duration | < 200 | fs | Ultrashort laser requirement for transient heating |
| Laser Spot Diameter (Pump/Probe) | 12 | µm | Spatial resolution required for TDTR |
| Thermal Penetration Depth | 1 | µm | Requirement for 1D heat transport modeling |
| Lattice $\kappa$ at Ambient P ($\text{Mg}{0.9}\text{Fe}{0.1}\text{O}$) | 5.7(6) | $\text{W}/(\text{m}\cdot\text{K})$ | Baseline measurement |
| Pressure Dependence Rate ($\text{Mg}{0.9}\text{Fe}{0.1}\text{O}$) | 6.1(7) | %/GPa | Determined pressure coefficient |
| Optical Source Spectral Range | 400 - 2400 | nm | Visible to near IR range for spectroscopic measurements |
Key Methodologies
Section titled “Key Methodologies”The complex measurements required highly controlled sample preparation and the use of SCD DACs optimized for both ultrafast pulsed laser techniques and broad-spectrum optical analysis.
- Sample Preparation & Polishing:
- Single-crystal minerals (Ferropericlase, Bridgmanite) were synthesized and subsequently polished down to extremely fine thicknesses (15 µm for TDTR samples, 25 µm for optical samples).
- Polishing utilized 3 µm diamond grit, followed by 0.3 µm alumina powder or 1 µm 3M diamond lapping film.
- Volatile Removal: Samples were thermally cleaned under vacuum at 1200 K for 15-30 minutes to eliminate hydroxides and surface contaminants, crucial for stable measurements.
- Transducer Deposition (TDTR): An 80 nm Aluminum (Al) film was coated onto one side of the ferropericlase sample via magnetron sputtering to act as the laser transducer for thermoreflectance.
- Pressure Cell Loading: Samples were loaded into symmetric DACs with ruby pressure calibrants, using Argon (Ar) or silicone oil as the pressure-transmitting medium.
- Lattice $\kappa$ Measurement (TDTR): Ultrafast mode-locked Ti:Sapphire oscillator (800 nm) provided pump and probe pulses. The time-delayed probe monitored reflectivity change in the Al film, allowing determination of heat transfer via bi-directional heat flow modeling.
- Radiative $\kappa_R$ Measurement (Spectroscopy): Optical absorption spectra were collected using a supercontinuum light source, optimized with all-mirror optics to avoid chromatic aberrations inherent in high-pressure DACs, enabling measurements from UV to mid-IR.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research highlights the indispensable role of precision diamond materials in high-pressure geophysics. 6CCVD’s expertise in customized MPCVD diamond directly addresses the requirements of this study and future high P-T experimentation.
Applicable Materials
Section titled “Applicable Materials”The successful replication and extension of this research depend entirely on the quality and engineering of the diamond components and films.
| Requirement in Paper | 6CCVD Material Solution | Specification Match |
|---|---|---|
| High-P SCD Anvils | Optical Grade Single Crystal Diamond (SCD) | Superior purity ensures low chromatic aberration and high signal-to-noise ratio in UV/Visible/IR spectroscopy. |
| High-Conductivity Samples | Conductive Boron-Doped Diamond (BDD) | Ideal for planned future experiments requiring conductive substrates or metallic layers at the core-mantle boundary (CMB). |
| Custom SCD Substrates | Single Crystal Diamond (SCD) Plates/Wafers | Available in thicknesses from 0.1 µm to 500 µm, perfectly matching the 15-25 µm sample requirements. |
| Large-Scale Studies | Polycrystalline Diamond (PCD) | Wafers available up to 125mm for scaling up related material science or semiconductor applications derived from high P-T findings. |
Customization Potential
Section titled “Customization Potential”The experimental success hinges on highly specific dimensions, surface quality, and functional coatings—all core 6CCVD capabilities.
- Precision Polishing for TDTR: The requirement for sub-micron polishing (0.3 µm grit) is exceeded by 6CCVD’s capability to achieve surface roughness Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD. This guarantees the necessary thermal and optical contact fidelity for TDTR measurements.
- Custom Metalization Transducers: The study required a precisely controlled 80 nm Al film. 6CCVD offers in-house magnetron sputtering and evaporation services for custom thin-film transducers, including:
- Metals: Au, Pt, Pd, Ti, W, Cu, and custom multi-layer stacks (e.g., Al for reflectivity transducers).
- Control: Thickness and uniformity control critical for reproducible TDTR modeling.
- Custom Dimensions and Etching: 6CCVD provides custom laser cutting and shaping for SCD anvils and sample substrates up to 125mm, ensuring compatibility with specialized DAC geometries.
Engineering Support
Section titled “Engineering Support”The paper identifies key unresolved issues regarding the effect of mass substitution, temperature dependencies, and sample morphology on thermal conductivity at relevant P-T conditions.
6CCVD’s in-house PhD engineering team specializes in diamond material science and high-pressure physics, offering dedicated consultation for projects aiming to:
- Optimize SCD Selection: Assisting researchers in selecting the ideal SCD grade (e.g., specific nitrogen concentration/purity) to minimize parasitic absorption and chromatic effects in optical spectroscopy systems.
- Develop High P-T Transducers: Designing thermally stable, pressure-resistant metalization schemes required for in situ measurements at high P-T conditions (e.g., 1000 K+).
- Material Integration: Providing guidance on integrating diamond elements (SCD anvils, BDD heat sinks) into complex experimental platforms like DACs and flash heating setups.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 1996 - Pressure dependence of the refractive index of diamond, cubic silicon carbide and cubic boron nitride [Crossref]
- 2007 - Measurement of thermal diffusivity at high pressure using a transient heating technique [Crossref]
- 2004 - Analysis of heat flow in layered structures for time-domain thermoreflectance [Crossref]
- 1996 - Thermal diffusivity of mantle minerals [Crossref]
- 2011 - Thermal conductivity of compressed H2O to 22GPa: a test of the Leibfried-Schlömann equation [Crossref]
- 1956 - Effect of radiative transfer on temperatures in the Earth [Crossref]
- 1957 - Radiative transfer in the Earth’s mantle
- 1998 - Thermal conductivity of MgO at high pressures
- 2013 - Effect of mass disorder on the lattice thermal conductivity of MgO periclase under pressure: implication for the deep earth heat flow
- 2009 - Thermal conductivity of MgO periclase from equilibrium first principles molecular dynamics [Crossref]