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Synthesis and thermionic properties of tungsten-barium titanate composites

机译：钛酸钨钡复合材料的合成及热电子性能

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摘要

The potential of novel tungsten-barium titanate composites as thermionic emitters is explored. Composites ranging from 20% to 80% tungsten by mass were prepared by sintering in an Ar-H_2 atmosphere. XRD and SEM studies indicate four major micro-constituents; W, BaTiO_3, Ba_4(Ti,Fe)_(12)O_(27) and BaWO_4. Richardson work functions (φ_R) and Richardson constants (A_R) were determined using a Schottky diode arrangement at temperatures ranging from 1223 to 1473 K. Work functions ranged from 2.67 eV to 3.32 eV with a shallow minimum at 40% by mass W and were relatively constant (～2.7-2.8 eV) in the range 30-70% by mass W. The decrease in work function was accompanied by a strong decrease in A_R from 39.3 A cm~(-2) K~(-2) to 0.02 A cm~(-2) K~(-2) over the range 20-70% by mass W. The reduction in both φ_R and A_R was associated with the major conversion of the surface to BaWO_4 and Ba_4Ti_(12)O_(27) during the activation treatment before emission testing.
机译：探索了新型钛酸钨钡复合材料作为热电子发射体的潜力。通过在Ar-H_2气氛中烧结制备钨的质量范围为20％至80％的复合材料。 XRD和SEM研究表明有四种主要的微成分。 W，BaTiO_3，Ba_4（Ti，Fe）_（12）O_（27）和BaWO_4。理查森功函数（φ_R）和理查森常数（A_R）是使用肖特基二极管装置在1223至1473 K的温度范围内确定的。功函数的范围从2.67 eV至3.32 eV，在40％质量W处具有较浅的最小值，并且相对较小常数（〜2.7-2.8 eV）在W的30-70％范围内。功函数的降低伴随着A_R的强烈降低，从39.3 A cm〜（-2）K〜（-2）降至0.02 A cm〜（-2）K〜（-2）在W的20-70％范围内。φ_R和A_R的减少均与表面向BaWO_4和Ba_4Ti_（12）O_（27）的主要转化有关。在排放测试之前的活化处理期间。

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