Thermopower of Sr₁₋ₓLaₓTiO₃ Ceramics

Titelangaben

Moos, Ralf ; Gnudi, Alain ; Härdtl, Karl Heinz:
Thermopower of Sr₁₋ₓLaₓTiO₃ Ceramics.
In: Journal of Applied Physics. Bd. 78 (1995) Heft 8 . - S. 5042-5047.
ISSN 1089-7550
DOI: https://doi.org/10.1063/1.359731

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Abstract

The thermopower η of Sr1−xLaxTiO3 ceramics was investigated up to x=0.5 and in the temperature range between 150 K and 1200 K. In addition, the carrier concentrationn was determined by Hall measurements and by a chemical Ti3+‐analysis. For low temperatures and high n, η depends linearly on temperature and on n −2/3, as expected from a degenerate quasi free electron gas. In the case of high temperatures and low n, the absolute value of η rises with 1.5⋅ln10⋅k/e per decade of temperature and with ln10⋅k/e per decade of carrier concentration, as expected from a classical broad‐band semiconductor obeying the Boltzmann statistics. In the range of degeneration an effective massm eff of 4.2 electron masses can be deduced without the assumption of a transport factor A_e. In the classical range A_e =3 can be evaluated, requiring only a temperature and lanthanum independent m eff. Thus, the thermopower of Sr1−xLaxTiO3ceramics can be described by a constant effective mass and a constant transport factor within a wide range of temperature and lanthanum content. Furthermore, the transition from degeneration to classical behavior can be described as a function of temperature and electron density, e.g., at room temperature it takes place at about x≊0.2 (i.e., n≊3.4⋅10^21/cm3).