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New Generation Multijunction Thermal Converters at Sandia National Laboratories

CPEM Digest (Conference on Precision Electromagnetic Measurements)

Johnson, Raegan L.; Meyrick, Aaron; Dominguez, Jason J.; Lukes, Karl L.; Stanford, Joshua S.; Cular, Stefan; O'Brien, Edward O.

Multijunction thermal converters are routinely used at many primary standards laboratories for ac voltage measurements and calibrations. After nearly two decades of inactivity, the Primary Standards Laboratory at Sandia National Laboratories has reestablished the process of fabricating silicon based multijunction thermal converters. Initial results indicate the devices perform similarly to devices fabricated circa 2001 with ac-dc differences of less than 2 mu mathrm{V}/mathrm{V} over the frequency range of 20 Hz to 20 kHz. From 20 kHz to 1 MHz, the ac-dc difference was higher, but remained below 200 mu mathrm{V}/mathrm{V}. In addition to presenting these results, new design considerations, such as high-resistivity substrates for high-frequency applications, are discussed.

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TYPE Conference Poster YEAR 2020
ScopusOSTI

Voltage-Controlled Bistable Thermal Conductivity in Suspended Ferroelectric Thin-Film Membranes

ACS Applied Materials and Interfaces

Foley, Brian M.; Wallace, Margeaux; Gaskins, John T.; Paisley, Elizabeth A.; Johnson, Raegan L.; Kim, Jong W.; Ryan, Philip J.; Trolier-Mckinstry, Susan; Hopkins, Patrick E.; Ihlefeld, Jon F.

Ferroelastic domain walls in ferroelectric materials possess two properties that are known to affect phonon transport: a change in crystallographic orientation and a lattice strain. Changing populations and spacing of nanoscale-spaced ferroelastic domain walls lead to the manipulation of phonon-scattering rates, enabling the control of thermal conduction at ambient temperatures. In the present work, lead zirconate titanate (PZT) thin-film membrane structures were fabricated to reduce mechanical clamping to the substrate and enable a subsequent increase in the ferroelastic domain wall mobility. Under application of an electric field, the thermal conductivity of PZT increases abruptly at ∼100 kV/cm by ∼13% owing to a reduction in the number of phonon-scattering domain walls in the thermal conduction path. The thermal conductivity modulation is rapid, repeatable, and discrete, resulting in a bistable state or a "digital" modulation scheme. The modulation of thermal conductivity due to changes in domain wall configuration is supported by polarization-field, mechanical stiffness, and in situ microdiffraction experiments. This work opens a path toward a new means to control phonons and phonon-mediated energy in a digital manner at room temperature using only an electric field.

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TYPE Journal Article YEAR 2018
ScopusOSTIDOI

VO2 thin films synthesis for collaborators and various applications

Johnson, Raegan L.; Clem, Paul G.

Vanadium dioxide (VO2) is an attractive material for a variety of applications due to its metal-to-insulator transition (MIT) observed at modest temperatures. This transition takes VO2 from its low temperature insulating monoclinic phase to a high temperature (above 68°C) metallic rutile phase. This transition gives rise to a change in resistivity up to 5 orders of magnitude and a change in complex refractive index (especially at IR wavelengths), which is of interest for radar circuit protection and tunable control of infrared signature. Recently, collaborations have been initiated between CINT scientists and external university programs. The Enhanced Surveillance funds help fund this work which enabled synthesis of VO2 films for several collaborations with internal and external researchers.

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TYPE Other Report YEAR 2016
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Fabrication of Wound Capacitors Using Flexible Alkali-Free Glass

IEEE Transactions on Components, Packaging and Manufacturing Technology

Wilke, Rudeger H.T.; Baker, Amanda; Brown-Shaklee, Harlan J.; Johnson, Raegan L.; Hettler, Chad H.; Murata, Takashi; O'Malley, Patrick D.; Perini, Steve; Lanagan, Michael

Alkali-free glasses, which exhibit high energy storage densities (~35 J/cc), present a unique opportunity to couple high temperature stability with high breakdown strength, and thus provide an avenue for capacitor applications with stringent temperature and power requirements. Realizing the potential of these materials in kilovolt class capacitors with >1 J/cc recoverable energy density requires novel packaging strategies that incorporate these extremely fragile dielectrics. In this paper, we demonstrate the feasibility of fabricating wound capacitors using 50-μm-thick glass. Two capacitors were fabricated from 2.8-m-long ribbons of thin (50 μm) glass wound into 125-140-mm-diameter spools. The capacitors exhibit a capacitance of 70-75 nF with loss tangents below 1%. The wound capacitors can operate up to 1 kV and show excellent temperature stability to 150 °C. By improving the end terminations, the self-resonance can be shifted to above 1 MHz, indicating that these materials may be useful for pulsed power applications with microsecond discharge times.

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TYPE Journal Article YEAR 2016
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Results 1–25 of 27
Results 1–25 of 27