New Thermionic Cathodes Coated with Ba-Ta-Zr-O-N System Produced by Carbothermal Reduction and Nitridation Process

Abstract

Ba (Ta_1-xZr_x)O_εN_δ compounds for x=0-1 were produced by carbothermal reduction and nitridationprocess. In this process, Ba (Ta_1-xZr_x)O_εN_δ and TaC as a second phase were observed by X-ray powderdiffraction patterns. Work functions and barium vaporization temperatures of the obtained powders wereestimated. Work functions of the Ba(Ta_1-xZr_x)O_εN_δ compounds increased with increasing zirconium content, and the value of 1.7eV for x=0.1 was less than that of 2eV with alkaline earth oxide. Barium in the Ba (Ta_1-xZr_x)O_εN_δ compound was volatile at higher temperature than that of authentic hot cathodes coatedwith alkaline earth oxide. In the 4.1mm of outside diameter, 3.3mm of inside diameter, and 100mm length of glasses with 9.3kPa of argon gas and mercury, some fluorescent lamps with hot cathodes coated with Ba (Ta_0.8Zr_0.2)O_2.2N_0.6 compound worked excellently and those has been lit for 61.2Ms, so far.