High-temperature Stability and Selective Thermal Emission of Polycrystalline Tantalum Photonic Crystals References and Links

We present the results of extensive characterization of selective emitters at high temperatures, including thermal emission measurements and thermal stability testing at 1000°C for 1h and 900°C for up to 144h. The selective emitters were fabricated as 2D photonic crystals (PhCs) on polycrystalline tantalum (Ta), targeting large-area applications in solid-state heat-to-electricity conversion. We characterized spectral emission as a function of temperature, observing very good selectivity of the emission as compared to flat Ta, with the emission of the PhC approaching the blackbody limit below the target cutoff wavelength of 2 μm, and a steep cutoff to low emission at longer wavelengths. In addition, we study the use of a thin, conformal layer (20 nm) of HfO 2 deposited by atomic layer deposition (ALD) as a surface protective coating, and confirm experimentally that it acts as a diffusion inhibitor and thermal barrier coating, and prevents the formation of Ta carbide on the surface. Furthermore, we tested the thermal stability of the nanostructured emitters and their optical properties before and after annealing, observing no degradation even after 144h (6 days) at 900°C, which demonstrates the suitability of these selective emitters for high-temperature applications. All-metallic three-dimensional photonic crystals with a large infrared bandgap, Metallic photonic band-gap materials, " Phys. Rev. A three-dimensional photonic crystal operating at infrared wavelengths, Modification of Planck blackbody radiation by photonic band-gap structures, " Phys. Rev. Toward high-energy-density, high-efficiency, and moderate-temperature chip-scale thermophotovoltaics, " Proc. Solar thermophotovoltaic converters based on tungsten emitters, " J. Radiation filters and emitters for the NIR based on periodically structured metal surfaces, " J. Thermophotovoltaic generation with selective radiators based on tungsten surface gratings, " Appl. Fan, " Tungsten black absorber for solar light with wide angular operation range, " Appl. Phys. Fabrication of two-dimensional tungsten photonic crystals for high-temperature applications, " J. Large-area fabrication of high aspect ratio tantalum photonic crystals for high-temperature selective emitters, " J. High-temperature resistive surface grating for spectral control of thermal radiation, " Appl. Thermal stability of micro-structured selective tungsten emitters, " AIP Conf. Fabrication of carbon/refractory metal nanocomposites as thermally stable metallic photonic crystals, " J. Electrodeposited 3D tungsten photonic crystal with enhanced thermal stability, " Chem. Optically matched trilevel resist process for nanostructure fabrication, " J. Meep: A flexible free-software package for electromagnetic simulations by the FDTD method, " Comput.