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1

Correlation between high-pressure electrical properties of ZrO2 and its crystallite size

Trefilova A. N., Korionov I. V., Babushkin A. N., Łojkowski W., Opalińska A.

Materials Science Poland

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2005

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Vol. 23, No. 1

247--252

EN

A relation between crystallite size and electrical properties of ZrO2 has been investigated by measurements of high-pressure electrical resistance. The resistance of nanocrystalline praseodymium-doped zirconia powders has been measured in the pressure and temperature ranges between 15 and 50 GPa, and 77 and 400 K, respectively. Around 30-37 GPa the resistances of all samples decrease by 3-4 orders of magnitude. Therefore, the anomalies in the pressure dependence of the resistance and of parameters depending on the concentration, mobility and activation energy of the charge carriers were found at ca. 40-45 GPa. The activation energy of the charge carriers depends on the crystallite size.

2

Transport phenomena in ammonium halides under high pressures

Tikhomirova G. V., Babushkin A. N.

Materials Science Poland

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2004

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Vol. 22, No. 2

131--135

EN

Polycrystalline ammonium chloride (NH4Cl), fluoride (NH4F) and bromide (NH4Br) were studied at pressures from 20 to 50 GPa in the temperature range of 77-400 K. Phase transitions from a highresistance to low-resistance state was found. The transition pressures were about 15 GPa for NH4Br, 27 GPa for NH4Cl, and 42 GPa for NH4F. The transition temperatures and pressures were shown to depend on the preliminary pressure treatment. All ammonium halides show metal-like behaviour under high pressures, similar to that of alkali halides.

3

Relaxation processes in ZrO2 at high pressures

Korionov I. V., Trefilova A. N., Babushkin A. N., Łojkowski W., Opalińska A.

Materials Science Poland

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2004

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Vol. 22, No. 3

241--244

EN

Relaxation processes in ZrO2 have been studied at pressures in the range of 22-50 GPa by measurements of high-pressure electrical relaxation of resistance in time. Electrical relaxation in nanocrystalline praseodymium doped zirconia powders and in a bulk material sample of zirconia has been measured in the pressure range from 35.5 to 50 GPa. The time dependence of electric resistance is most precisely described by exponential function up to the pressure of 35.5-50 GPa. The time dependence of electric resistance is most precisely described by exponential function up to the pressure 44-45.5 GPa. After treatment the pressure higher than 45.5 GPa, the character of the relaxation changes and resistance increased with time. Relaxation processes have not been observed in ZrO2 with 56 nm crystallite sizes.