A Proposal for a Composite with Temperature-Independent Thermophysical Properties: HfV2–HfV2O7

Materials, vol. 13, pp. 5021

Abstract

The HfV2–HfV2O7 composite is proposed as a material with potentially temperature-independent thermophysical properties due to the combination of anomalously increasing thermoelastic constants of HfV2 with the negative thermal expansion of HfV2O7. Based on literature data, the coexistence of both a near-zero temperature coefficient of elasticity and a coefficient of thermal expansion is suggested for a composite with a phase fraction of approximately 30 vol.% HfV2 and 70 vol.% HfV2O7. To produce HfV2–HfV2O7 composites, two synthesis pathways were investigated: (1) annealing of sputtered HfV2 films in air to form HfV2O7 oxide on the surface and (2) sputtering of HfV2O7/HfV2 bilayers. The high oxygen mobility in HfV2 is suggested to inhibit the formation of crystalline HfV2–HfV2O7 composites by annealing HfV2 in air due to oxygen-incorporation-induced amorphization of HfV2. Reducing the formation temperature of crystalline HfV2O7 from 550 °C, as obtained upon annealing, to 300 °C using reactive sputtering enables the synthesis of crystalline bilayered HfV2–HfV2O7.

Authors 7

1. Philipp Keuter corresponding Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

2. Anna L. Ravensburg Aachen Materials Chemistry

   RWTH Aachen University · Uppsala University

   Affiliation as printed

   Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

3. Marcus Hans Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

4. Soheil Karimi Aghda Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

5. Damian M. Holzapfel Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

6. Daniel Primetzhofer

   Uppsala University

   Affiliation as printed

   Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden

7. Jochen M. Schneider Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany