Electron emission from ceramic materials produced by phase transitions

Abstract

Summary form only given. One limit to the performance of high power microwave (HPM) sources is the cathode technology. An alternate method that is currently under investigation is to create a rapid polarization change by changing the phase of a polar dielectric. Two examples of a phase transition are paraelectric to ferroelectric and antiferroelectric to ferroelectric. In both cases, the material is heated to a temperature close to the transition and a pulsed electric field is used to switch the phase. Experiments are conducted using a demountable high vacuum triode with disk shaped ceramic materials. The disks are 1 mm thick by 15 mm in diameter. The material compositions under investigation include 8/65/35 (Pb,La)(Zr,Ti)O/sub 3/ (PLZT) ferroelectrics, antiferroelectrics, and hard ferroelectric Pb(Zr,Ti)O/sub 3/ piezo-ceramic materials. The samples under test are gridded with an evaporated gold film that is patterned with circular apertures. The grid is pulsed with a solid state drive coupled with a step up pulse transformer. A DC voltage (up to 20 kV) is applied to the anode to accelerate any carriers liberated from the gridded surface.