Dispenser　cathodes　are　the　most　widely　used　electron　emission　source　in　vacuum　electron　devices.　The　impregnant　is　the　source　for　producing　active　substances　in　the　dispenser　cathodes,　which　play　an　irreplaceable　role.　However,　impregnants’　phase　structure　and　optical　response　properties　have　yet　to　be　systematically　investigated.　Herein,　four　aluminates　were　prepared　as　impregnants　via　homogeneous-lyophilization　followed　by　calcination.　Due　to　the　unique　preparation　process,　the　elemental　distribution　of　aluminates　is　exceptionally　uniform.　Based　on　the　first-principles　DFT　calculations,　the　primary　phases　of　the　two　aluminates　532　and　411　were　confirmed　to　be　(Ba0.61Ca0.39)3Al2O6　(P213)　and　(Ba0.75Ca0.25)4Al2O7　(Cmca).　At　the　same　time,　α-Ba2ScAlO5　and　β-Ba2ScAlO5　are　the　only　phases　of　aluminates　411-0.75Sc　and　411-1.25Sc,　respectively.　XPS　confirmed　two　chemical　states　of　Ba　and　Sc　in　the　aluminates.　FT-IR　and　27Al　NMR　indicate　that　the　aluminum-oxygen　skeleton　in　all　aluminates　exists　mainly　as　[AlO4]　tetrahedrons,　accompanied　by　a　small　amount　of　distorted　[AlOx]　(x　=　5,　6)　polyhedrons.　The　UV–visible　light　absorption　capacity,　band　gap　and　intra-structural　electron　transfer　capacity　of　all　aluminates　are　determined　by　UV–Vis　DRS　and　PL　spectra.　The　dispenser　cathodes　impregnated　with　aluminates　532　and　411　have　zero-field　current　densities　of　5.3　A/cm2　and　14.3　A/cm2　at　1100°Cb,　respectively.　The　dispenser　cathodes　impregnated　with　aluminate　containing　scandium　have　different　space-charge-limited　current　densities,　i.e.,　29.48　A/cm2　for　411-0.75Sc　and　13.66　A/cm2　for　411-1.25Sc　at　1000°Cb.　This　work　will　provide　more　options　for　synthesizing　and　applying　impregnants.　©　2024