Semiconducting phases in the system YLaxBa2-xCu3O7- (x=1.0-0.0) exhibit three-dimensional variable-range hopping conduction over a wide temperature (T) range (100-900 K). Thermopower (S) measurements support this observation. S increases with T for x=1.0 and 0.8 indicative of transport at the chemical potential E. The decrease in S with T for x=0.4 and 0.3 is indicative of gap at E. A schematic band picture is used to explain the observed behaviors. © 1995 The American Physical Society.

Upadhyayula V Varadaraju

Department Of Chemistry

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Physical Review B

Ba2BiInO6 is a semiconductor which can be derived from Ba2Bi3+Bi5+O6 by substituting all the Bi3+ ions. Presently we report on the isovalent substitution of Sb5+ at Bi5+ site. Sb acts as a sintering aid as well as a dopant. Doping results in an increase in the resistivity as well as thermopower. All the doped compositions show degenerate semiconducting behavior at high temperature. The highest figure of merit obtained is 2.4×10-5 K-1 at 770 K for the x = 0.06 composition. © 2009 Elsevier Ltd. All rights reserved.

Solid State Communications

Effect of isovalent doping on the high temperature thermopower and resistivity properties of Ba2 BiInO6

Systematic studies on the (Formula presented) ((Formula presented) system were carried out in order to determine the effect of the rare-earth ionic size and magnetic moment on the (Formula presented) suppression rate. The phases were characterized by powder x-ray diffraction (XRD), resistivity, and ac susceptibility measurements. XRD studies indicate a higher solubility limit of (Formula presented) ions in the (Formula presented) system as compared to the (Formula presented) system. Resistivity and ac susceptibility studies indicate that the (Formula presented) suppression rate for a given (Formula presented) ion depends on the ionic radius of the rare earth ((Formula presented)) and is higher for larger rare earths. The trend in (Formula presented) suppression as a function of concentration ((Formula presented)) shows deviation from Abrikosov-Gorșkov behavior. A metal-insulator transition is observed at higher dopant concentrations, and the semiconducting phases are found to obey the Mottșs variable range hopping mechanism of conduction. The parameters related to hopping conduction; viz., the characteristic temperature ((Formula presented)), localization length ((Formula presented)), hopping range ((Formula presented)), and hop energy ((Formula presented)) have been calculated, and a comparative study of the variation of these parameters in the two systems has been made. © 1996 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Effect of ion substitution in the) system: Implications of ion dependence and disorder

Hopping conductivity in fully oxygenatedPrBa2Cu3Oy,YBa2Cu2CoOy, andPrBa2Cu2CoOy

Modern Problems in Condensed Matter Sciences Hopping Transport in Solids

The Hopping Thermopower

Application of the polaron-transport theory to σ(ω) inTl2Ba2Ca1−xGdxCu2O8,YBa2Cu3O7−δ, andLa2−xSrxCuO4

Thermoelectric power of high-Tcsuperconductors

Synthetic Metals

Photogenerated carriers in La2CuO4, YBa2Cu3O7−δ and Tl2Ba2Ca(1 − x)GdxCu2O8: Polarizability-induced pairing of polarons

Observation of variable-range hopping up to 900 K in the YLaxBa2-xCu3O7- system

Journal	Physical Review B
ISSN	01631829
Open Access	No