Effect of Sc₂O₃-Doping on Thermal Emission Properties of Y₂O₃-Gd₂O₃-HfO₂ Thermal Cathode

The Sc₂O₃-doped Y₂O₃-Gd₂O₃-HfO₂ coatings, an advanced direct-heating cathode material with excellent thermal emission properties, were synthesized via solid state reaction of refractory and rare-earth metal oxides.The influence of the Sc₂O₃-doping on the thermal emission properties of Y₂O₃-Gd₂O₃-HfO₂ coatings was investigated with scanning electron microscopy and energy dispersive spectroscopy.The results show that the Sc₂O₃-doping effectively increased the emission current density of the cathode.To be specific, doping with 10% (wt) Sc₂O₃ increased the emission current density up to 5.3 A/cm² at 1500℃, 35.5% higher than that of the un-doped cathode.The free Sc atoms, possibly released in formation of Sc₂O₃ and Y₂O₃ solid solution and considerably increasing the conductivity of Y₂O₃-Gd₂O₃-HfO₂ coatings, explained the mechanism responsible for the significant enhancement of thermal emission current density.