Structural and thermionic emission investigations of perovskite BaHfO3 based low work function emitters

Abstract

Low work function materials are attracting researchers worldwide as potential thermionic emitters or collectors. In this study, a number of composite cathodes using a promising perovskite, barium hafnate (BaHfO3) with tungsten (W), lanthanum hexaboride (LaB6) and gadolinium hexaboride (GdB6) were investigated for thermionic properties. A series of cylindrical pellets using W-BaHfO3 and BaHfO3-hexaborides were milled, pressed, and then sintered at 1600 °C for 4 h. The structural, morphological, chemical, and thermionic properties of the synthesised emitters were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), electron dispersive spectroscopy (EDS), and a Schottky apparatus. The Work function for W-BaHfO3 cathodes is found to decrease with increasing W proportion, with a minimum of 2.97 ± 0.06 eV for the sample having 70% W. Lower work function values of 2.21 ± 0.13 and 1.68 ± 0.03 eV, respectively, are observed for the LaB6-20% BaHfO3 and GdB6- 20% BaHfO3 cathodes.