Study On The Room-temperature Solid-state Reaction Method For Preparing Aluminates For Impregnant Cathodes

Vacuum devices have important applications not only in radar imaging,missile defense and electronic countermeasures,but also in satellite communications and navigation,deep space exploration and other civil and scientific research fields.Cathodes,as the heart of microwave vacuum electronic devices,and its performance directly determines the characteristics and life of vacuum devices.Dispenser cathodes are widely used as the electron emission source in vacuum electronic devices.However,as the core material for impregnated dispenser cathodes,aluminates and their preparation process and material properties are still insufficiently studied.The traditional preparation methods of aluminate precursors include mechanical mixing method and liquid phase co-precipitation method.In this paper,aluminate precursors were prepared by solid-state method at room temperature.The phase structure and micro-morphology were analyzed by X-ray diffraction?XRD?and scanning electron microscopy?SEM?,the emission properties of the experimental cathode were measured by a diode device.The main conclusions are as follows:?1?The phase structure of the aluminate precursor prepared by the room temperature solid-state method mainly comprises an?-?Ba,Ca?CO3 crystal phase and an amorphous?or poorly crystalline??-AlOOH phase.The results of Field Emission Scanning Electron Microscope showed that the particle sizes of?-?Ba,Ca?CO3 and?-AlOOH phases in precursor are on the order of submicron and nanometer respectively.?2?During the preparation of 612 aluminates by solid-phase method at room temperature,Ba₅CaAl₄O₁₂ phase would gradually transition to Ba₃CaAl₂O₇ phase with the increase of BaO content;the increase of CaO content in a certain range is beneficial to the formation of Ba₃CaAl₂O₇ phase,but if the content Too high,the aluminate appears mainly as a Ba₅CaAl₄O₁₂ structure.The morphology analysis showed that the formed aluminate particles were in the submicron range and the morphology was consistent.?3?Flat-panel diode test results showed that the corresponding cathode emission current density of 612 aluminate prepared by solid-state method at room temperature increases with the increase of BaO content.When BaO content is x=6.8,the maximum current emission can reach 7.1 A/cm² at 1130?in x BaO:1CaO:2Al₂O₃ series aluminates.In addition,in 6BaO:x CaO:2Al₂O₃ series aluminates,with the increase of CaO content,the corresponding cathode emission current density increases first and then decreases.And when CaO content is x=1.3,the maximum current emission is 7.2 A/cm²at 1130?.In conclusion,the aluminate prepared by solid-state reaction at room temperature has uniform morphology and structure,and the emission performance of the experimental cathode prepared by this method is similar to that of the experimental cathode prepared by liquid phase method.This method does not need solvent,has less environmental pollution,simple operation and is easy to industrialize,and has great potential application and popularization value.