First principles investigation of structural, electronic, elastic and thermal properties of rare-earth-doped titanate Ln2TiO5

Abstract

Systematic first-principles calculations based on density functional theory were performed on a wide range of Ln2TiO5 compositions (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Y) in order to investigate their structural, elastic, electronic, and thermal properties. At low temperature, these compounds crystallize in orthorhombic structures with a Pnma symmetry, and the calculated equilibrium structural parameters agree well with experimental results. A complete set of elastic parameters including elastic constants, Hill's bulk moduli, Young's moduli, shear moduli and Poisson's ratio were calculated. All Ln2TiO5 are ductile in nature. Analysis of densities of states and charge densities and electron localization functions suggests that the oxide bonds are highly ionic with some degree of covalency in the Ti-O bonds. Thermal properties including the mean sound velocity, Debye temperature, and minimum thermal conductivity were obtained from the elastic constants

Firing salts method for the synthesis of orthorhombic Gd2TiO5: experimental characterization supported by DFT first principles calculations

“…The Rietveld refinement, figure 2, confirms the formation of the almost pure orthorhombic Gd 2 TiO 5 phase with lattice parameters a = 10.489 Å, b = 3.761 Å and c = 11.321 Å; in concordance with those previous reported values for the orthorhombic Gd 2 TiO 5 phase (table 1) [4,12,30], and with those calculated from the geometric optimization. According to the Rietveld results, the most distorted cation coordination is around the Gd1 site, because of the short interatomic Gd-O1 distance (1.794 Å), with a 30% difference between the 7-fold different oxygen ions while the Ti cation, tetrahedrally coordinated, have a maximal 10% difference between Ti-O2 compared against the different oxygen interatomic distances, as shown in table 1.…”

Utilizing rare earth titanates to improve performance of solid-state electrochromic device

“…The peak profile of the refinement was fitted with a 6-parameter polynomial background and pseudo-Voigt function. The GTO was found to exist in the orthorhombic phase with the Pnam [36,38,51] space group at room temperature. In order to visualize the crystal structure of the prepared sample, VESTA software was used (figure 1(b): inset).…”

“…Perovskite materials are known for their diffusion dominance property and can be further explored for this purpose by appropriately designing a device [35]. The lanthanide titanates [36][37][38] of composition Ln 2 TiO 5 (Ln = Lanthanide) exhibit various exciting properties of high dielectric constant [39] and thermal stability [40]. As Ln 2 TiO 5 is known to show applicable dielectric properties, this motivates us to analyze the doping effect of diffusion-controlled electroactive materials on the performance of the solid-state electrochromic device.…”