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Chapter 6
The changes in optical properties of the HO/air sample compared to e.g. H O/O can
2
2
2
be explained by two phenomena:
1. An increased transmission from 1000-2400 nm: this can be explained by a
decrease of the carrier concentration. This is supported by the change in carrier
concentration as observed in the electrical measurements.
2. The disappearance of the fringes (350-950 nm) as well as decreased reflection
(1700-2400 nm): this can be explained by increased scattering caused by
increased void formation of the ZnO:Al at the glass/ZnO:Al interface, due to
the dissolution of the ZnO:Al.
6.4.3.5 Proposed reaction products
Reference [25] proposes the formation of the major corrosion products of zinc under
sheltered conditions and shows a reaction sequence from zinc hydroxide to the
chlorides and sulphates. It is suggested that Zn(OH) is not very stable and reacts to
2
hydrozincite. In the presence of sulphur or chlorine, the hydrozincite can be replaced.
Next steps might lead to the formation of sodium containing compounds and
products containing both sulphate and chlorine. Since it is concluded that Zn(OH)
2
can form from ZnO, Figure 6.18 shows a possible reaction scheme for the degradation
of the grain boundaries in zinc oxide.
Since carbon and sulphur are mainly found in the top of the samples in the SIMS
Figure 6.18
General reaction scheme for the degradation of zinc oxide based on reference [25].
measurements, it is expected that the hydroxycarbonate and the hydroxysulphate
are surface compounds. However, the chloride-compounds and the hydroxide will
be present in a larger piece of the sample and therefore have a larger impact on the
change in the electrical parameters.
206
The changes in optical properties of the HO/air sample compared to e.g. H O/O can
2
2
2
be explained by two phenomena:
1. An increased transmission from 1000-2400 nm: this can be explained by a
decrease of the carrier concentration. This is supported by the change in carrier
concentration as observed in the electrical measurements.
2. The disappearance of the fringes (350-950 nm) as well as decreased reflection
(1700-2400 nm): this can be explained by increased scattering caused by
increased void formation of the ZnO:Al at the glass/ZnO:Al interface, due to
the dissolution of the ZnO:Al.
6.4.3.5 Proposed reaction products
Reference [25] proposes the formation of the major corrosion products of zinc under
sheltered conditions and shows a reaction sequence from zinc hydroxide to the
chlorides and sulphates. It is suggested that Zn(OH) is not very stable and reacts to
2
hydrozincite. In the presence of sulphur or chlorine, the hydrozincite can be replaced.
Next steps might lead to the formation of sodium containing compounds and
products containing both sulphate and chlorine. Since it is concluded that Zn(OH)
2
can form from ZnO, Figure 6.18 shows a possible reaction scheme for the degradation
of the grain boundaries in zinc oxide.
Since carbon and sulphur are mainly found in the top of the samples in the SIMS
Figure 6.18
General reaction scheme for the degradation of zinc oxide based on reference [25].
measurements, it is expected that the hydroxycarbonate and the hydroxysulphate
are surface compounds. However, the chloride-compounds and the hydroxide will
be present in a larger piece of the sample and therefore have a larger impact on the
change in the electrical parameters.
206
