Dielectric Properties of Plasma-Sprayed Fully Natural Garnets

Various kinds of natural garnets belonging to the almandine type (3FeO·Al2O3·3SiO2) were sprayed by plasma spray technique to build coatings on metallic substrates. The experimental garnet powders came from different mines in the Czech Republic and Mongolia. After coating and cooling the substrates...

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Bibliographic Details
Published in:Coatings (Basel) 2022-07, Vol.12 (7), p.1017
Main Authors: Ctibor, Pavel, Sedláček, Josef, Straka, Libor
Format: Article
Language:English
Subjects:
Aluminum oxide
Chemical composition
Coatings
Dielectric properties
Direct current
Garnets
Low voltage
Mechanical properties
Microhardness
Near infrared radiation
Plasma
Protective coatings
Radiation
Raw materials
Reflectance
Scanning electron microscopy
Substrates
Thermal cycling
Wear resistance
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Summary:Various kinds of natural garnets belonging to the almandine type (3FeO·Al2O3·3SiO2) were sprayed by plasma spray technique to build coatings on metallic substrates. The experimental garnet powders came from different mines in the Czech Republic and Mongolia. After coating and cooling the substrates were removed. In this way, self-supporting plates were obtained and further studied with microscopy, X-ray diffraction, and dielectric spectroscopy. Mechanical properties were in our focus as well. Microhardness was measured on cross sections dedicated to microstructure observation. Wear resistance in wet conditions was tested in a slurry. Reflectance was measured applying visible and infrared (VIS-NIR) radiation. Dielectric properties of coatings were studied at low voltage capacitance, loss tangent and also under direct current (DC) resistance. The results show that garnet minerals are interesting candidates for various optical and electronic applications; they have similar dielectric behavior as, for example, aluminum oxide or similar high-purity synthetic oxides, and, simultaneously, they have extraordinarily low reflectance in VIS-NIR radiation. The differences between natural powders and resulting coatings are discussed in connection with their chemical and phase compositions.
ISSN:2079-6412
2079-6412
DOI:10.3390/coatings12071017