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Transport properties of as-deposited cadmium phthalocyanine Schottky-barrier devices

100%

Samuel M. , Menon C. S. , Unnikrishnan N. V.

Materials Science Poland

2007

tom Vol. 25, No. 1

177--184

Sandwich samples of the type (Au-CdPc-Al) have been fabricated by successive vacuum deposition of gold (Au), cadmium phthalocyanine (CdPc), and aluminium (Al) thin films on glass substrates. Good rectification properties have been observed in the device. Ohmic conduction in the lower voltage range has been identified from the forward bias current density-voltage characteristics at room temperature. At higher voltages, a space charge limited conductivity (SCLC) controlled by an exponential trapping distribution above the valence band edge has been observed. The transport properties of the material at ambient temperature have been obtained from an analysis of the samples in the SCLC region. Schottky emission has been identified at lower voltages from the analysis of the reverse bias characteristics.

La1-xSrxCo1-y-zFeyNizO3 perovskites - possible new cathode materials for intermediate-temperature solid-oxide fuel cells

84%

Świerczek K. , Marzec J. , Molenda J.

Materials Science Poland

2006

tom Vol. 24, No. 1

115--122

La1-xSrxCo1-y-zFeyNizO3 perovskites have been synthesized with hexagonal R-3c structures by a modified citric acid method and determined their structural and transport properties. Structural instabilities for samples with high Ni and Sr content heated to 1270 K were observed, leading to the appearance of secondary phases with spinel structures. Moessbauer studies revealed the presence of two different, clearly distinguishable surroundings of Fe ions, despite single crystallographic positions of iron ions. Low-temperature (77-300 K) dc conductivity and thermoelectric power measurements suggest an activated charge transport mechanism with the activation energy strongly dependent on the chemical composition of the material. Electrical conductivity as a function of temperature suggests the appearance of a hopping mechanism. The observed hightemperature (870-1070 K) dc electrical conductivity of La1-xSrxCo1-y-zFeyNizO3 samples is relatively high and strongly depends on chemical composition. It seems possible to optimise the transport properties of La1-xSrxCo1-y-zFeyNizO3 by chemical composition, which may lead to a new, attractive cathode material in terms of possible applications in intermediate -temperature solid-oxide fuel cells (IT-SOFCs).