It
has
been well
established that the boron volatility from
sealing glass-ceramics plays an important role on the forma-
tion of LaBO3 on the surface of cathode.
17,19,22 To investigate
the volatility of sealing glass-ceramics, the weight change of
glass-ceramics in dry air at different temperatures is measured
as a function of time for up to 7 days, as shown in Fig. 2a
and b. It is worth noting that the accumulated weight change of
glass-ceramics at each temperature is proportional to the square
root of heat-treatment time. This indicates that the volatility
of glass-ceramics is a diffusion-controlled process.
23 In addi-
tion, the accumulated weight change of glass-ceramics increases
with increasing Bi2O3 content. For examples, the accumulated
weight change of glass-ceramics held at 800 ◦C for 7 days
increases from 1.12% cm−2 for glass#2Bi2O3 to 1.93% cm−2
for glass#9Bi2O3.