Radiation induced electrical degradation in crystalline Al2O3: a bulk effect

Zong, Xu; Shen, Cheng-Fu; Liu, Song; Wu, Zhong-chi; Chen, Yi; Zhang, Renjun; Zhu, Jane G.; Chen, Y.; Evans, Bruce D.; González, R.; Sellers, C. H.

doi:10.1016/0022-3115(94)00397-1

Cited by 7 publications

(7 citation statements)

References 20 publications

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“…27,39 Also enhanced diffusion and conduction along grain boundaries have been presumed responsible for apparent RIED effects. 34 One observation of large electrical conductivity increases after electron irradiation by Zong et al [16][17][18] is possibly to be excluded from the present criticism. The authors did not use an electric guard ring.…”

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confidence: 79%

Difficulties in measuring electrical conductivities in highly insulating materials: Radiation-induced electrical degradation is an artifact

Kesternich

2000

J. Mater. Res.

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Measurement of the electrical conductivity in high-resistance insulators is made difficult by previously unrecognized limits in the electric guarding technique. Electron irradiation experiments on single-crystalline Al 2 O 3 , performed for studying the effects of irradiation on the electrical conductivity, revealed that radiation-induced electrical degradation effects in ceramic insulators, previously reported to occur after electron, ion, and neutron irradiation, are an artifact.Electrical conductivity is induced in insulating materials during ionizing irradiations as a result of the creation of electron-hole pairs. The effect is called radiation-induced conductivity (RIC). 1 RIC requires a continuous production of electron-hole pairs. Hence RIC ceases when the radiation is terminated, and after some transient time the insulating property of the material is restored. As a result of fast particle irradiations, an additional, but permanent, rise in conductivity was reported, termed radiation-induced electrical degradation (RIED). Researchers have claimed that RIED occurs when the irradiations are performed with the specimen exposed to an electric field (>30 V/mm for single-crystal Al 2 O 3 ) and at elevated temperature. 2,3 In contrast to RIC, RIED is considered highly detrimental for the use of insulator materials under irradiation, since the observed conductivity increases were cumulative.In single-and polycrystalline aluminium oxide, RIED was reported after electron, 4 -9 ion, 10 and neutron 11 irradiations. Electrical resistivity losses up to ten orders of magnitude were reported. Later, however, the existence of RIED was questioned. 12 Because of the high importance of RIED for the use of insulating materials in future fusion reactors, many experiments have since been carried out resulting in arguments for and against RIED. 13-42 As a compromise between the contradictory positions, it was suggested that the exact brand of the insulating material might determine whether RIED occurs or not, since the conductivity of insulators is sensitively dependent on the type and concentration of impurity atoms. 43 It was also suggested that the existence of RIED might depend on the type of irradiating particle. 43 Particularly for electron irradiations, where the majority of results in favor of RIED exists, 4 -9,13,14,16-18 a clarifying experiment was missing.In the present investigation, an electron irradiation experiment in search of RIED was performed on exactly the same specimen material and close to the same irradiation conditions for which RIED had been repeatedly observed and reported. 5,8,9,13,14 (The experiment was performed following the suggestions of an International Energy Agency (IEA) workshop on radiation effects in ceramic insulators. 43 ) The specimen material was part of an Al 2 O 3 single crystal (Union Carbide UV grade), provided by Dr. E.R. Hodgson, to either verify or disprove the RIED results that were obtained on another part of this same crystal.Two slices of about 2-mm thickness were cut from the...

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confidence: 79%

Difficulties in measuring electrical conductivities in highly insulating materials: Radiation-induced electrical degradation is an artifact

Kesternich

2000

J. Mater. Res.

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“…The procedure for processing the contacts has been reported. 5,6 With an applied electric field of 1800 V/cm ͑along the c axis͒, the central region of the sample was irradiated with 1.8 MeV electrons in air at a dose rate of 4 A/cm 2 at 773 K. A two-terminal electrical technique was used for conductivity measurements. The electron irradiation was carried out with a vertical Van de Graaff.…”

Section: Methodsmentioning

confidence: 99%

“…The electron beam was collimated such that the periphery of the sample was shielded from the beam. 5,6 Samples for transmission electron microscope ͑TEM͒ observations were cut ultrasonically to a diameter of about 50 m by dimpler ͑Model D500͒ and were thinned by dual ion mill ͑Gatan Model 600͒ until a small hole appeared.…”

Section: Methodsmentioning

confidence: 99%

“…5 Oxygen interstitials are unstable at 573 K. 14,15 Therefore, at 773 K few anion vacancies can survive because the cross section for interstitial-vacancy recombination far exceeds that of production. 6 Photochemical processes prevail primarily in alkali halides. 16 There has been no evidence that atomic displacement events of indigenous ions in ␣-Al 2 O 3 and MgO occur via photochemical processes.…”

Section: Point Defectsmentioning

confidence: 99%

“…3, 4 Hodgson 3 reported that concurrent ionization and elasticcollision events are necessary for RIED to occur, based on his observation that RIED depended on the bombarding electron energy. Subsequently Zong et al 5,6 established the following: first, RIED is associated with dislocations generated during Rad-E-T, second, RIED was induced by electrons and holes from ionizing radiation and not from displacement damage by elastic collisions with energetic electrons.…”

Section: Introductionmentioning

confidence: 99%

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Model for radiation-induced electrical degradation of α-Al2O3cr

et al. 1996

Phys. Rev. B

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When a ceramic oxide with an applied electric field is subjected to extended irradiation with energetic particles at elevated temperatures, the electrical conductivity has been reported to increase, a phenomenon termed radiation-induced electrical degradation ͑RIED͒. In the present study ␣-Al 2 O 3 crystals were subjected to 1800 V/cm while irradiated with 1.8 MeV electrons at 773 K. Above a critical dose the conductivity increased. During the conductivity enhancement, the applied field was reversed, resulting in a decrease in the conductivity. This result demonstrates that RIED was caused by carriers injected from the electrodes, in concert with electrons and holes created during ionizing irradiation. A model for RIED is proposed: the injected carriers are trapped mainly at impurities near the electrodes, leading to formation of dislocations. These dislocations serve as traps for electrons and holes generated during ionizing radiation. A network of interconnecting dislocations is associated with the enhanced conductivity.

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A review of the optical properties of anion lattice vacancies, and electrical conduction in α-Al2O3: their relation to radiation-induced electrical degradation

Evans¹

1995

Journal of Nuclear Materials

216

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Radiation induced electrical degradation in crystalline Al2O3: a bulk effect

Cited by 7 publications

References 20 publications

Difficulties in measuring electrical conductivities in highly insulating materials: Radiation-induced electrical degradation is an artifact

Difficulties in measuring electrical conductivities in highly insulating materials: Radiation-induced electrical degradation is an artifact

Model for radiation-induced electrical degradation of α-Al2O3cr

A review of the optical properties of anion lattice vacancies, and electrical conduction in α-Al2O3: their relation to radiation-induced electrical degradation

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