TY - JOUR
T1 - High temperature protonic conduction in LaPO4 doped with alkaline earth metals
AU - Amezawa, Koji
AU - Tomii, Yoichi
AU - Yamamoto, Naoichi
N1 - Funding Information:
A part of this work was carried out under the financial support by the Nippon Sheet Glass Foundation and by a Grant-in-Aid from the Japanese Ministry of Education, Culture, Sports, Science and Technology. Dr. H. Miyamoto and Mr. Y. Nishikawa at the Technology Research Institute of Osaka Prefecture, Japan, are acknowledged for their help on material preparation.
PY - 2005/1/14
Y1 - 2005/1/14
N2 - Electrical conduction in the monazite-type LaPO4 doped with 1 mol% of alkaline earth metals (Mg, Ca, Sr, and Ba) was investigated by using conductivity measurements under 0.4-5 kPa of p(H2 O) and 0.01-100 kPa of p(O2) at 500-925°C. The Sr-doped LaPO4 exhibited highest conductivities among the four samples. Conductivities of the Ca-doped LaPO4 were in same levels as those of the Sr-doped sample, but the Ba-doped LaPO4 showed conductivities in almost half magnitude compared with the Sr- and Ca-doped samples. Conductivities of the Mg-doped LaPO4 were much lower than those of the other doped samples, and were comparable with those of the undoped LaPO4. From humidity dependence and H/D isotope effect of the conductivity, it was found that the Ca-, Sr-, and Ba-doped LaPO4 conducted protons dominantly under moisturized conditions, whereas the Mg-doped LaPO4 did not show significant protonic conduction. The differences in conduction properties depending on the doped alkaline earth metals could be basically interpreted by the differences in the solubility of the alkaline earth metals into LaPO4. The p(H 2O) and p(O2) dependencies of the conductivities of the Ca-, Sr-, and Ba-doped LaPO4 were finally discussed in terms of defect equilibria.
AB - Electrical conduction in the monazite-type LaPO4 doped with 1 mol% of alkaline earth metals (Mg, Ca, Sr, and Ba) was investigated by using conductivity measurements under 0.4-5 kPa of p(H2 O) and 0.01-100 kPa of p(O2) at 500-925°C. The Sr-doped LaPO4 exhibited highest conductivities among the four samples. Conductivities of the Ca-doped LaPO4 were in same levels as those of the Sr-doped sample, but the Ba-doped LaPO4 showed conductivities in almost half magnitude compared with the Sr- and Ca-doped samples. Conductivities of the Mg-doped LaPO4 were much lower than those of the other doped samples, and were comparable with those of the undoped LaPO4. From humidity dependence and H/D isotope effect of the conductivity, it was found that the Ca-, Sr-, and Ba-doped LaPO4 conducted protons dominantly under moisturized conditions, whereas the Mg-doped LaPO4 did not show significant protonic conduction. The differences in conduction properties depending on the doped alkaline earth metals could be basically interpreted by the differences in the solubility of the alkaline earth metals into LaPO4. The p(H 2O) and p(O2) dependencies of the conductivities of the Ca-, Sr-, and Ba-doped LaPO4 were finally discussed in terms of defect equilibria.
KW - Alkaline earth metal
KW - Chemical compound
KW - LaPO
KW - Monazite
KW - Orthophosphate
KW - Protonic conduction
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U2 - 10.1016/j.ssi.2004.07.003
DO - 10.1016/j.ssi.2004.07.003
M3 - Article
AN - SCOPUS:9644263956
VL - 176
SP - 135
EP - 141
JO - Solid State Ionics
JF - Solid State Ionics
SN - 0167-2738
IS - 1-2
ER -