Thermochromism of sputter-deposited vanadium oxyfluoride coatings

Conference · Mon Dec 31 04:00:00 EST 1990

OSTI ID:86078

Khan, K A; Granqvist, C G ^[1]

---

1. Chalmers Univ. of Technology, Gothenburg (Sweden). Physics Dept.

Thermochromism offers interesting possibilities for controlling the radiative throughput through windows, as well as for numerous other applications. The purpose of this brief paper is to point at the potential and prospects of using sputter-deposited vanadium oxyfluoride coatings. A thermochromic coating, suitable for energy-efficient windows, is characterized by a transmittance which drops as the temperature goes above a certain comfort temperature.Thermochromism in VO{sub 2}-based materials is well known; it is connected with a reversible structural transition from a low-temperature monoclinic phase to a high-temperature phase with metallic-like properties. The metallic phase is characterized by a plasma wavelength at {approximately} 1 {mu}m. Hence it is possible to accomplish a temperature-dependent modulation of the near-infrared transmittance. In order to produce a practically useful window coating, the VO{sub 2}-based material must be processed suitably. The authors discuss how magnetron sputtering can be used for (potential) large-area deposition. Among the many alternative approaches for depressing the phase change temperature they note the replacement of oxygen by fluorine and the introduction of stress either from the substrate or from a suitable overlayer. The work reported here deals with fluorination through reactive sputter deposition. A key result, reported below, is that the fluorination leads to a significant decrease of the luminous absorptance. Finally, it may be that a practical window coating must invoke a three-layer design with a VO{sub 2}-based coating embedded between antireflecting dielectric layers; this latter point will not be pursued further here.

• OSTI ID: 86078
• Report Number(s): CONF-8809123--; ISBN 0-8194-0069-6
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
36 MATERIALS SCIENCE
DESIGN
ELECTRICAL PROPERTIES
GLAZING MATERIALS
OPTICAL PROPERTIES
OXYFLUORIDES
PERFORMANCE
PHYSICAL PROPERTIES
VANADIUM COMPOUNDS
WINDOWS