Lattice parameters and electronic bandgap of orthorhombic potassium sodium niobate K$$_{0.5}$$Na$$_{0.5}$$NbO$$_{3}$$ from density-functional theory

Abstract

We perform a theoretical analysis of the structural and electronic properties of sodium potassium niobate K$$_{1-x}$$ 1 - x Na$$_{x}$$ x NbO$$_{3}$$ 3 in the orthorhombic room-temperature phase, based on density-functional theory in combination with the supercell approach. Our results for $$x=0$$ x = 0 and $$x=0.5$$ x = 0.5 are in very good agreement with experimental measurements and establish that the lattice parameters decrease linearly with increasing Na contents, disproving earlier theoretical studies based on the virtual-crystal approximation that claimed a highly nonlinear behavior with a significant structural distortion and volume reduction in K$$_{0.5}$$ 0.5 Na$$_{0.5}$$ 0.5 NbO$$_{3}$$ 3 compared to both end members of the solid solution. Furthermore, we find that the electronic bandgap varies very little between $$x=0$$ x = 0 and $$x=0.5$$ x = 0.5 , reflecting the small changes in the lattice parameters. Graphic abstract

Computational Screening of Oxide Perovskites as Insertion‐Type Cathode Material

“…To the best of our knowledge MgNbO 3 has never been synthesised, but similar niobate perovskites have been discussed in literature. For instance, ceramic materials within the solid-solution K x Na 1Àx NbO 3 (0 < x < 1) have been studied due to their promising piezoelectric properties, [78,79] and LiNbO 3 is known for its ferroelectricity and its optical properties. [80] Even more interesting, high ionic Li mobility was achieved in the defective perovskite material Li x La ð1ÀxÞ=3 NbO 3 , [81][82][83] but the research has not been extended to other shuttle ions.…”

“…To the best of our knowledge has never been synthesised, but similar niobate perovskites have been discussed in literature. For instance, ceramic materials within the solid‐solution (0 < x < 1) have been studied due to their promising piezoelectric properties, [ 78,79 ] and is known for its ferroelectricity and its optical properties. [ 80 ] Even more interesting, high ionic Li mobility was achieved in the defective perovskite material …”

Computational Screening of Oxide Perovskites as Insertion-Type Cathode Material

“…To the best of our knowledge MgNbO 3 has never been synthesised, but similar niobate perovskites have been discussed in literature. For instance, ceramic materials within the solid solution K x Na 1 -x NbO 3 (0<x<1) have been studied due to their promising piezoelectric properties 74,75 and LiNbO 3 is known for its ferroelectricity and its optical properties. 76 Even more interesting, high ionic Li mobility was achieved in the defective perovskite material Li x La (1 -x)/3 NbO 3 , 77-79 but the research has not been extended to other shuttle ions.…”