Experimental Research on the Relation between the Electric Breakdown Strength of Some Alkali-hahides Crystals and Temperature at Both D-c and A-c Voltages
Liu Fu-yei
This paper introduces the researches on the variation of the electric breakdown
strength of some alkali halides crystals with temperature.Frohlich's theories of
electric breakdown strength of crystals at both low and high temperatures are
briefly mentioned.The experimental results of various foreign authors are also
reviewed.
The breakdown tests on NaCl and KBr crystalsl under both d.c.and a.c.
voltages are described.We use the specimen with one side recessed,both sides of
which are sprayed under vacauum with metallic alluminum as electrodes;it is
then placed in an electrode system,which as a whole is enclosed in a metallic
chamber filled with nitrogen gas at about 30 atm.for breakdown test.Results
obtained show that under d.c.voltage the maximum electric breakdown strength
of NaCl is about 1.5×10~6 v/cm at about 50℃.,while that of KBr 0.95×10~6
v/cm at about 120℃.Under a.c.,the electric breakdown strength of NaCl
is lower than that under d.c.
The phenomenon of variation of breakdown strength with temperature can be
explained by means of Frohlich's theories as mentioned above,while the difference
of electric breakdown strength between d.c.and a.c.voltages is tentatively assumed
to be due to the effects of ionic and electronic space charges.
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