Electrical properties in C3N4 under high pressure

Alexey N. Babushkin 1O. L. Kobeleva 1V. N. Khabashesku 3E. N. Yakovlev 4V. V. Milyavskiy 2

1. Ural State University, Department of Physics, Lenin Av., 51, Ekaterinburg 620083, Russian Federation
2. High Energy Density Research Center SA, IVTAN RAS, Izhorskaya 13/19, Moscow 127412, Russian Federation
3. Rice University, 6100 Main St., Houston, TX 77005, United States
4. Institute for High Pressure Physics RAS, Troitsk 142190, Russian Federation


During a resent years a grate attention was given to the problem of an investigation of phase transitions in C3N4 as by M.L.Cohen and co-authors were theoretical predicted the diamond-like properties of beta-C3N4. We investigated the phase transitions in the two samples of this material, which were prepared by different methods (chemical (1) and shock (2)), in the carbonado-diamond anvil cell with using the methods of electrical measurement on d.c. and impedance spectroscopy. The first sample were investigated at pressure 15GPa-43GPa, a second sample at pressure less 33GPa. A dependences of the electrical resistances R of the samples at the T=300K, in the 103Hz<f<8*105 Hz were made. A hodographs of impedance and a tangency of an angle of dielectric loss dependencies were got.
For the sample No.1. impedance measurement give a little hysteresis and a weak indication on the existence of phase transitions at 15GPa-25GPa and 33GPa-35GPa. After unloading the sample on 2-4-cycles input-output, the R is sharply increased more than 104 times and large hysteresis is appeared (d.c.). After holding under pressure 43GPa during 6 days hysteresis has vanished. After fast increasing of pressure till 43GPa (2 minutes) some reaction has taken place and after unloading was got a graphite dust and transparent small crystallite of unknown nature. The preliminary results obtained shows the new phase appearing from C3N4 under pressure till 43GPa at room temperature and phase transitions under 15-25GPa and 33-35GPa possible with changing composition. For the sample No.2. the results are differ from results for sample No.1. The resistance is decreasing with increase the pressure.
So the method of preparing samples and their purity is essential for behavior their electrical conductivity.
This work in part has been supported by RFBR (grant No.01-03-96494,02-03-32699), CRDF (grant No.REC-005).

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Presentation: poster at E-MRS Fall Meeting 2003, Symposium F, by Olga L. Kobeleva
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-27 10:38
Revised:   2009-06-08 12:55
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