J. Michiels et Ka. Gschneidner, EFFECT OF LONG-TERM HEAT-TREATMENT ON THE ELECTRICAL-PROPERTIES OF RSE1.47 (R=LA AND ND) AND LASE1.48, Journal of applied physics, 82(10), 1997, pp. 4952-4956
The phase stability of the gamma-cubic LaSe1.47, LaSe1.48 and NdSe1.47
compounds with the Th3P4 type structure, along with their electrical
resistivity, Seebeck coefficient, and Hall effect were measured period
ically as the materials were annealed at 800 degrees C or 1000 degrees
C to determine their potential as thermoelectric materials for long t
erm applications at high temperatures. The LaSex samples showed the pr
esence of the ternary oxide La10Se14O (beta-phase), The content of thi
s phase; increased with increasing anneal time, whereas the NdSe1.47 s
amples showed no sign of a ternary oxide second phase. The room temper
ature electrical resistivity and Seebeck coefficient of LaSe, increase
d with increased annealing time, while those of NdSe1.47 decreased, Th
e power factors remained relatively stable with annealing time. The hi
gh temperature electrical resistivity of LaSe1.47 and NdSe1.47 increas
ed with increasing temperature up to 1000 degrees C, while the Seebeck
coefficient became more negative. The power factor, however, peaks at
800 degrees C for LaSe1.47 and at 500 degrees C for NdSe1.47. Based a
n this study we find that LaSex is not a promising high temperature th
ermoelectric material due to the formation of the beta-phase, whereas
the NdSe1.47 which does not form the P-phase oxide is a potential cand
idate material. (C) 1997 American Institute of Physics.