A cation vacancy center in crystalline Al<sub>2</sub>O<sub>3</sub>

Evans, Bruce D.; Cain, L. S.

doi:10.1080/10420159508227241

Cited by 15 publications

(13 citation statements)

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“…Normalized attenuation data in sapphire comparing the results of this work at 500 h (at 1400°C) to previous heated experiments by Gryvnak and Burch (at 1500°C) 4 and a previous room‐temperature oxygen ion implantation experiment by Evans and Cain …”

Section: Resultsmentioning

confidence: 68%

“…Figure shows the broadband added attenuation measured in this work at 500 h (the end of the period of time with temperature held at 1400°C) normalized so that the measured added attenuation at 500 nm (the wavelength at which a peak was observed in the added attenuation data) is equal to one. Figure also shows the digitized spectral attenuation data from Gryvnak and Burch (heating bulk sapphire crystals to 1500°C) and from Evans and Cain (room‐temperature oxygen ion implantation in bulk sapphire) . The data sets from these previous works were also normalized so that the values of the measured attenuation are equal to one at 500 nm.…”

Section: Resultsmentioning

confidence: 99%

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In Situ Thermally Induced Attenuation in Sapphire Optical Fibers Heated to 1400°C

Petrie

Blue

2014

J. Am. Ceram. Soc.

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The purpose of this work was to determine the spectral loss of sapphire optical fibers as a function of temperature to determine the suitability of using sapphire optical fiber‐based instrumentation in extremely high‐temperature applications such as coal gasifers, or potentially in advanced high‐temperature nuclear reactors. In this work, the broadband (450–2200 nm) optical attenuation of two commercially available sapphire optical fibers was monitored in situ as the fibers were heated in steps to temperatures up to 1400°C. The results presented in this work are the first known reporting of the broadband spectral loss in sapphire fibers (as opposed to bulk sapphire) as a function of temperature. The added attenuation in the sapphire fibers seemed to reach a steady‐state at temperatures of 1300°C and below, and remained below 3.7 dB/m at all measurable wavelengths. At 1400°C, rapid increases in attenuation were observed that appeared to increase as the square root of heating time, indicating a diffusion‐limited process. Cooling to room temperature in steps resulted in recovery of a large portion of the thermally induced attenuation, suggesting that the effects caused by heating at 1400°C introduced additional attenuation that was very temperature dependent. Based on comparison with previous work and on the spectral features of the added attenuation observed in this work, heating at 1400°C could have caused high‐temperature oxidation of the sapphire fibers, which resulted in a temperature‐dependent scattering loss mechanism.

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Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

In Situ Thermally Induced Attenuation in Sapphire Optical Fibers Heated to 1400°C

Petrie

Blue

2014

J. Am. Ceram. Soc.

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“…The sapphire-to-silica splices were located above the furnace and above the reactor core so that the silica lead fibers were not heated and were only exposed to minimal (estimated to be less than 10% of the peak gamma dose rate in the facility) amounts of gamma radiation. To account for changes in the transmission of the Composite of aluminum vacancies with a charge of À1 or À2 and aluminum vacancies with a trapped OH À ion and a trapped hole 3.0 413 [4,[11][12][13][14] sapphire fiber assembly due to attenuation in the silica lead fibers, a jacketed silica control fiber (of the same type as the lead fibers that were spliced to the sapphire fibers) was also loaded into the experiment. This control fiber was bent through 180 degrees at the location of the sapphire-to-silica splices and then passed back up to the top of the irradiation facility.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

“…Previous work by Crawford, 2 Valbis, and Itoh, 3 and Evans et al 4 offer more detailed overviews of lattice defects and color centers in sapphire. [5][6][7][8][9][10][11][12][13][14] The determination of the specific defect centers that are responsible for each of the numerous absorption bands that have been observed in irradiated sapphire crystals has not been universally accepted in the scientific community. [5][6][7][8][9][10][11][12][13][14] The determination of the specific defect centers that are responsible for each of the numerous absorption bands that have been observed in irradiated sapphire crystals has not been universally accepted in the scientific community.…”

Section: Introductionmentioning

confidence: 99%

“…A summary of the major defect centers that have been identified in sapphire is shown in Table I, along with the peak absorption energies (and wavelengths) for each defect center. [5][6][7][8][9][10][11][12][13][14] The determination of the specific defect centers that are responsible for each of the numerous absorption bands that have been observed in irradiated sapphire crystals has not been universally accepted in the scientific community. The data that are compiled in Table I summarize the most generally accepted assignments of defects to various absorption bands.…”

Section: Introductionmentioning

confidence: 99%

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In Situ Gamma Radiation‐Induced Attenuation in Sapphire Optical Fibers Heated to 1000°C

2014

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The purpose of this work was to determine the suitability of using instrumentation utilizing sapphire optical fibers in a high‐temperature gamma radiation environment. In this work, the broadband (500–2200 nm, or 0.56–2.48 eV) optical attenuation of commercially available sapphire optical fibers was monitored in situ during continuous gamma irradiation from room temperature up to 1000°C. The gamma dose rate of the irradiation facility was measured to be 370 rad/h (dose in sapphire). Results show rapid growth of an absorption band centered below 500 nm (the minimum detectable wavelength in this work) and extending as far as ~1000 nm that reached a dynamic equilibrium after approximately 4 h of irradiation at room temperature. Increasing temperature generally reduced the added attenuation, although the added attenuation came to a nonzero equilibrium at temperatures of 1000°C and below. No peaks in the added attenuation were observed above 1000 nm, and the added attenuation at 1300 and 1550 nm remained less than 0.7 dB throughout the entire experiment. Fitting the attenuation spectra to Gaussian functions at each temperature revealed a large absorption band near 3 eV that monotonically decreased both in magnitude and width with increasing temperature. A second smaller band near 1.73 eV monotonically increased in both magnitude and width with increasing temperature, suggesting that some interconversion between defects may be occurring at higher temperatures.

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The Behavior of Radiation Damage of Nb+ Ion Implanted Sapphire after Annealing at Reducing Atmosphere

Huang

Neubeck

Yamamoto

et al. 1998

phys. stat. sol. (a)

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Sapphire crystals with (0001) and (011‐2) orientations were implanted with 380 keV Nb+ ions to a dose of 5×1016 ions/cm2 at room temperature and 100 K. The behavior of the radiation damage produced by ion implantation followed by annealing with a series of steps from 500 to 1100 °C at reducing atmosphere is investigated using optical absorption technique. The absorption curves were evaluated by Gaussian fitting based on the well known F‐type centers, which were confirmed by luminescence measurements. The results of optical density (OD) from the bands with annealing temperature and time show that the annealing behavior of the radiation damage produced by Nb+ ion implantation can be divided into three stages. The first stage is in the range of annealing from 500 to 800 to 900 °C; the second is from 900 to 1000 °C, the third is one above 1000 °C. Defects were annealed within these stages due to different mechanisms which are proposed on the basis of the optical absorption measurements combined with the observation of SEM micrographs and colour variation of the sample after annealing steps with temperature.

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A cation vacancy center in crystalline Al₂O₃

Cited by 15 publications

References 3 publications

In Situ Thermally Induced Attenuation in Sapphire Optical Fibers Heated to 1400°C

In Situ Thermally Induced Attenuation in Sapphire Optical Fibers Heated to 1400°C

In Situ Gamma Radiation‐Induced Attenuation in Sapphire Optical Fibers Heated to 1000°C

The Behavior of Radiation Damage of Nb+ Ion Implanted Sapphire after Annealing at Reducing Atmosphere

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A cation vacancy center in crystalline Al2O3

Cited by 15 publications

References 3 publications

In Situ Thermally Induced Attenuation in Sapphire Optical Fibers Heated to 1400°C

In Situ Thermally Induced Attenuation in Sapphire Optical Fibers Heated to 1400°C

In Situ Gamma Radiation‐Induced Attenuation in Sapphire Optical Fibers Heated to 1000°C

The Behavior of Radiation Damage of Nb+ Ion Implanted Sapphire after Annealing at Reducing Atmosphere

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A cation vacancy center in crystalline Al₂O₃