Study on the plasma sprayed amorphous diopside and annealed fine-grained crystalline diopside

Natural diopside CaMgSi2O6 was processed by plasma spray technique into self-supporting plates. The experimental powder for spraying came from as-mined natural diopside and was crushed and sieved to the proper size for plasma spraying with a water-stabilized plasma torch (WSP). By removing the substrates after cooling, self-supporting plates (SSP) were obtained. These deposits were further studied with optical microscopy, SEM, X-ray diffraction, thermal analysis, mechanical tests and dielectric spectroscopy. Microhardness was measured on cross-sections prepared for microstructure observation. Wear resistance in wet conditions was tested as well. Dielectric properties of capacitor samples prepared from the self-supporting sprayed deposits were measured at low voltage. The results showed that diopside is an interesting candidate for various electrical applications as it has similar dielectric behavior as alumina or silicates. Thermal annealing of the SSP was done. Despite crystallization of the amorphous fraction (present after spraying) into a fine-grained structure, annealing worsened slightly dielectric responses of diopside. Differences between diopside and other silicates sprayed by the authors in the past are discussed.