2026-09-23T19:11:01Zhttps://api.repository.cam.ac.uk/server/oai/requestoai:www.repository.cam.ac.uk:1810/3310202025-04-08T15:15:04Zcom_1810_198332com_1810_256064col_1810_214775
Dielectric Breakdown of Silver Azide
10.17863/CAM.78465
Tang, Tong, Bor
The breakdown of single crystals of heavy metal azides has been investigated.
In silver azide, the low-field conduction is by mobile interstitial
cations and their enthalpies ,of formation and hopping have been determined
from the Arrhenius plot of the conductivity. Based on AC conductivity ยท
measurements and the observed time dependence of the current, it is shown
that ionic polarisations occur at the electrode interfaces. With fields
higher than 15 kV.m- l (for silver or carbon electrodes) bipolar field injection
i s though t to take place. These fields can lead to dielectric breakdown,
although the incubation period may l as t up to several days - but less than a
second if the field is 0.4 MV.m- l or higher. Evolution of nitrogen has been
measured by mass spectrometry under this condition. Based on a comparison
with thermal decomposition of AgN 3 , the following mechanism is proposed.
for the 'electrical decomposition'. Holes injected from the anode combine
bi-molecularly via traps and produce N2. Some of the electrons from the
cathode arc localised at impurity centres or defects . The discharge of mobile
Ag+ at the electron traps results in silver atoms which, if formed on the
surface , may migrate as well as aggregate because of their high diffusivity
even at room temperature. By optical and electron microscopy silver nuclei
have been detected on the surface of a crystal to which a strong field is
applied through conducting contacts. It has also been observed that post-breakdown
disruption in the form of an explosion occurs. The breakdown is
explained as due to the formation on the crystal surface of filamentlike
silver films, and the initiation of deflagration and subsequent detonation,
to the appearance along the metallic conduction path of 'hot spots' arising
from Joule heating and leading to thermal decomposition and self-heating.
This explanation is supported by evidence such as initiation locality.
In the comprehensive study on the thermal decomposition of AgN 3, new
methods have been proposed for the analysis of kinetic data, both isothermal
and dynamic, from solid state reactions.
Parallel observations, in less detail, suggest that dielectric breakdown
and explosion initiation by similar mechanisms occur in thallous and
probably in lead azides. It is a possibility that breakdown of long incubation
period can be brought about by analogous 'electrical decomposition'
processes in certain metal halides, oxides, hydrides , alkali azides and other
ionic metal compounds, although in substances which are not highly exothermic
no explosion will follow the breakdown.
University of Cambridge
1979-04
Thesis
doctoral
PhD
en
https://www.repository.cam.ac.uk/handle/1810/331020
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azides
conductivity
decomposition