Fabrication and thermoelectricity of La _{1-x} (Ca, RE) _{x} VO _{3} (⩽ x ⩽ 1) composition-spread films

Abstract

La1−x(Ca, RE)xVO3 (0x1) composition-spread films were fabricated successfully by Combinatorial Pulsed Laser Deposition (CPLD). The structures and thermoelectric (TE) properties of the films were evaluated paralelly by Con- current X-ray Diffraction (CXRD) and Multi-channel Thermoelectric Measurement systems respectively. The CXRD (200) peaks of the composition-spread films changed linearly, which indicated that the composition-spread films formed solid solu- tion in the whole composition range (0 x 1). The effects of oxygen content and the substitutions of Ca and rare earth (RE: Ce, Nd, Eu) ions on TE properties of LaVO3 were also analysed respectively. There was little change in the Seebeck coefficients of LaVO3 films grown at different growth temperatures, while the resistivity decreased with the enhance of the growth temperatures. The largest power factor (0.7 μW/cm K 2 )o f LaVO3 film was obtained at 800 ◦ C, while the valence of vanadium ion changed from 3+ to 2+ because of the lack of oxygen. With the increase of the content of Ca 2+ ions, the valence of vanadium ion changed from 3+ to 4+, which was responsible for the decrease of TE properties in La1-xCaxVO3 system. The substitution of RE (Ce, Nd, Eu) ions for La ions changed not only Seebeck coefficient but also resistivity, but power factor (α) was not increased obviously. In La1-xCexVO3 system, La ion took 3+, and Ce ion took 3+ although Ce 4+ was stable in theory, which caused the valence of V ion not changed as expected from 3+ to 2+. The reason may be that the size of Ce 3+ ion is similar to that of La 3+ ion, so Ce takes the valence of 3+ easily in LaVO3.