Untitled

Prospects for Engineering Thermoelectric Properties in La1/3NbO3 Ceramics Revealed via Atomic-Level Characterization and Modeling

“…Experimental X-ray diffraction patterns of the LNO compound presented in this work are, in agreement with literature, 29,49 indexed based on the orthorhombic structure, using the Cmmm space group and a ≈ 2a perovskite , b ≈ 2a perovskite , and c ≈ 2a perovskite , as shown in Figure 1. The experimental X-ray data were refined using structural files available in the literature: two independently-derived structure files, namely ICSD 90692 and 150448 (corresponding to…”

“…The structure was shown to transform to a tetragonal symmetry, P4/mmm with a ≈ a perovskite , b ≈ a perovskite , and c ≈ 2a perovskite , at 195°C, being stable up to 500°C. These structures were further supported by subsequent diffraction studies 29,50 , while electron diffraction studies carried out by Garcia-Martin et al 51 showed the presence of superlattice reflections in the electron diffraction patterns, indicating a doubling of the c-axis. The same study showed the presence of diffuse satellite reflections attributed to the presence of a modulated structure.…”

“…The structural parameters for the simulations were taken from Ref. 29 The Seebeck coefficient and electrical conductivity were measured simultaneously using a ULVAC ZEM 3 in helium atmosphere. Thermal conductivity was obtained by measuring the density (Archimedes method), thermal diffusivity (using a custom-built apparatus in argon atmosphere) and heat capacity (Netzsch STA 449C; nitrogen atmosphere).…”

“…Refs 29,49 , respectively), were used for completeness, yielding similar goodness of fits. The lattice parameters, fractional coordinates, site occupancies and isotropic thermal parameters are listed in Table S1 of the Supplementary Information provided.…”

Structure for perovskites with layered ordering of A-site cations

“…Evidently, these re¯ections were not observed in the initial X-ray studies (Iyer & Smith, 1967). These re¯ections were seen in electron diffraction patterns (Carrillo et al, 2000), from which the structure was determined as orthorhombic in Cmmm on a 2 Â 2 Â 2 cell. 5 They were also seen in a recent neutron study (Dilanian et al, 2000), where re®nement led to a structure for La 1/3 NbO 3 that is essentially identical with the structure of La 2/3 TiO 3 (Fig.…”