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6CCVD Research

Modulation calorimetry in diamond anvil cells. II. Joule-heating design and prototypes

At a Glance

Section titled ā€œAt a Glanceā€
MetadataDetails
Publication Date2017-04-10
JournalJournal of Applied Physics
AuthorsZachary M. Geballe, Viktor V. Struzhkin, Andrew Townley, Raymond Jeanloz
InstitutionsCarnegie Institution for Science, University of California, Berkeley
Citations2

Abstract

Section titled ā€œAbstractā€

Part I shows that quantitative measurements of heat capacity are theoretically possible inside diamond anvil cells via high-frequency Joule heating (100 kHz-10 MHz), opening up the possibility of new methods to detect and characterize transformations at high-pressure such as the glass transitions, melting, magnetic orderings, and the onset of superconductivity. Here, we test the possibility outlined in Part I, using prototypes and detailed numerical models. First, a coupled electrical-thermal numerical model shows that specific heat of metals inside diamond cells can be measured directly using āˆ¼1 MHz frequency, with <10% accuracy. Second, we test physical models of high-pressure experiments, i.e., diamond-cell mock-ups. Metal foils of 2-6 Ī¼m-thickness are clamped between glass insulation inside diamond anvil cells. Fitting data from 10 Hz to āˆ¼30 kHz, we infer the specific heat capacities of Fe, Pt, and Ni with Ā±20%-30% accuracy. The electrical test equipment generates āˆ’80 dBc spurious harmonics, which overwhelm the thermally induced harmonics at higher frequencies, disallowing the high precision expected from numerical models. An alternative Joule-heating calorimetry experiment, on the other hand, does allow absolute measurements with <10% accuracy, despite the āˆ’80 dBc spurious harmonics: the measurement of thermal effusivity, Ļck (Ļ, c, and k being density, specific heat, and thermal conductivity), of the insulation surrounding a thin-film heater. Using a āˆ¼50 nm-thick Pt heater surrounded by glass and 10 Hz-300 kHz frequency, we measure thermal effusivity with Ā±6% accuracy inside the sample chamber of a diamond anvil cell.

Tech Support

Section titled ā€œTech Supportā€

Original Source

Section titled ā€œOriginal Sourceā€

References

Section titled ā€œReferencesā€
  1. 2004 - Modulation Calorimetry: Theory and Applications

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