Probing the Electronic Structures of Ternary Perovskite and Pyrochlore Oxides Containing Sn⁴⁺ or Sb⁵⁺

Abstract

Experimental and computational studies were performed to understand the electronic structure of ternary perovskites (ASnO(3), A = Ca, Sr, Ba, Cd), pyrochlores (RE(2)Sn(2)O(7), RE = Y, La, Lu; Cd(2)Sb(2)O(7)), and defect pyrochlore oxides (Ag(2)Sb(2)O(6)) containing the main group ions Sn(4+) and Sb(5+). In all compounds, the lowest energy states in the conduction band arise primarily from the antibonding Sn/Sb 5s-O 2p interaction. In the alkaline-earth stannate perovskites (BaSnO(3), SrSnO(3), and CaSnO(3)) the conduction bandwidth decreases strongly in response to the octahedral tilting distortion triggered by the decreasing size of the alkaline-earth cation. This in turn leads to a corresponding increase in the band gap from 3.1 eV in BaSnO(3) to 4.4 eV in CaSnO(3). The band gap of CdSnO(3) is relatively small (3.0 eV) considering the large octahedral tilting distortion. The origin of this apparent anomaly is the mixing between the empty Cd 5s orbitals and the antibonding Sn 5s-O 2p states. This mixing leads to a widening of the conduction band and a corresponding decrease in the band gap. The participation of the normally inert A-site cation in the electronic structure near the Fermi level can be considered an inductive effect, as it utilizes substitution on the A-site to directly modify the electronic structure of the SnO(3)(2)(-) framework. While the pyrochlore structure is more complicated, the energy level and width of the lowest energy conduction band can be analyzed in a manner similar to that utilized on the perovskite structure. The Sn-O-Sn and Sb-O-Sb bonds are highly distorted from linear geometry in pyrochlore, leading to a relatively narrow conduction band and a wide band gap. In Cd(2)Sb(2)O(7) and Ag(2)Sb(2)O(6) the Cd(2+) and Ag(+) ions exhibit a strong inductive effect that widens the conduction band and lowers the band gap significantly, very similar to the effect observed in the perovskite form of CdSnO(3).

CaSnO 3 obtained by modified Pechini method applied in the photocatalytic degradation of an azo dye

“…The Eg value obtained for the CaSnO 3 sample was estimated to be 4.2 eV, according to Equation A [22,23]. This result is similar to the experimental value (4.40 eV) reported in [29], and slightly smaller than the theoretical band gap value of 4.87 eV reported in [30].…”

Thermal properties of the orthorhombic CaSnO3 perovskite under pressure from ab initio quasi-harmonic calculations

“…At ambient conditions, CaSnO 3 exhibits a orthorhombic GdFeO 3 -type perovskite structure belonging to the P bnm space group, which is expected to be stable up to pressures of about 40 GPa and temperatures of about 2000 K [25]. Other phases have been reported (ilmenite-like, hexagonal, rhombohedral, tetragonal and cubic) [26][27][28][29], the orthorhombic one remaining the most studied [30][31][32][33][34][35][36][37][38]. Many fundamental properties of this material, however, still have to be reliably determined, which is the case of its thermal properties (its thermal structural and elastic features, its thermodynamic behavior, etc.).…”

High-mobility BaSnO3 grown by oxide molecular beam epitaxy

“…The recent discovery 4,5 of room temperature mobilities of ∼300 cm 2 V −1 s −1 in doped single crystals of La-doped BaSnO 3 has therefore generated tremendous excitement. 6 In combination with its wide bandgap (∼3 eV 7 ), this makes BaSnO 3 of immediate interest as a new transparent conducting oxide and as a wide bandgap semiconductor for power electronics. Furthermore, for the first time, it would be possible to integrate functional perovskite oxides, such as ferroelectrics or strongly correlated oxides, on a lattice-and symmetry-matched, high-mobility semiconductor.…”