ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Electrical conductivity, σ, Seebeck coefficient, S, and dielectric constant, ε, measurements on the pressed pellets of six light rare-earth orthochromites, RCrO3, where R = La, Pr, Nd, Sm, Eu and Gd, have been carried out in the temperature range 300 to 1000 K. These are essentially electronic conductors, exhibiting p-type extrinsic semiconducting nature in the studied temperature range. The extrinsic charge carriers (holes) originate from Cr4+ centres which are present due to native defects in these solids. Their room-temperature electrical conductivities lie in the range 10−7 to 10−5 Ω−1 cm−1, which become of the order of 10−2 Ω−1 cm−1 near 1000 K. The conductivity is a maximum in LaCrO3 and drops across the RCrO3 series, with SmCrO3 being an exception. The mechanism involved in the electrical transport is the hopping of holes from Cr4+ centres to neighbouring Cr3+ ions. The activation energy of transport is nearly 0.3 eV. Typical hopping mobility of the holes is of the order of 102 cm−2 V−1 sec−1 at 325 K and of the order of 10 cm2 V−1 sec−1 at 1000 K. The mobility activation energy of the holes in a typcial RCrO3 decreases with temperature due to the smoothing of the potential barriers between Cr4+ and Cr3+ sites. Several discontinuities are observed in the σT against T −1 and S against T −1 plots of RCrO3. The anomalies which these discontinuities reflect here have also been indicated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00540784
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