Directionally Solidified Cobalt-Doped MgO-MgAl<sub>2</sub>O<sub>4</sub> Eutectic Composites for Selective Emitters
Cobalt-doped MgO-MgAl<sub>2</sub>O<sub>4</sub> eutectic composites were explored for their use as selective emitters for thermophotovoltaic devices. Eutectic ceramic rods with different cobalt content were directionally solidified by using the laser floating zone technique at...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-10-01
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| Series: | Applied Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3417/12/20/10254 |
| Summary: | Cobalt-doped MgO-MgAl<sub>2</sub>O<sub>4</sub> eutectic composites were explored for their use as selective emitters for thermophotovoltaic devices. Eutectic ceramic rods with different cobalt content were directionally solidified by using the laser floating zone technique at two processing rates to obtain microstructures with different domain sizes. Thermal emission between 1000 °C and 1500 °C and optical properties (reflectance and transmittance) at room temperature were measured in the Co-doped composites and the effect on microstructure and cobalt content was investigated. Thermal emission consisted of an intense broad band at about 1.67 µm matching with the bandgap of the InGaAs cell. The emission was ascribed to the de-excitation from the <sup>4</sup>T<sub>1</sub>(F) multiplet to the <sup>4</sup>A<sub>2</sub>(F) ground state of the thermally excited Co ions located in the tetrahedral sites of the MgAl<sub>2</sub>O<sub>4</sub> phase. The selectivity of the thermal emission showed a decrease with the cobalt content due to the enhancement of other electronic transitions, which leads to keeping the cobalt content in these composites at low levels (<0.15% at Co) for their use as selective emitters. |
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| ISSN: | 2076-3417 |