A Partial Anion Disorder in SrVO2H Induced by Biaxial Tensile Strain

Abstract

SrVO2H, obtained by a topochemical reaction of SrVO3 perovskite using CaH2, is an anion-ordered phase with hydride anions exclusively at the apical site. In this study, we conducted a CaH2 reduction of SrVO3 thin films epitaxially grown on KTaO3 (KTO) substrates. When reacted at 530 °C for 12 h, we observed an intermediate phase characterized by a smaller tetragonality of c/a = 0.96 (vs. c/a = 0.93 for SrVO2H), while a longer reaction of 24 h resulted in the known phase of SrVO2H. This fact suggests that the intermediate phase is a metastable state stabilized by applying tensile strain from the KTO substrate (1.4%). In addition, secondary ion mass spectrometry (SIMS) revealed that the intermediate phase has a hydrogen content close to that of SrVO2H, suggesting a partially disordered anion arrangement. Such kinetic trapping of an intermediate state by biaxial epitaxial strain not only helps to acquire a new state of matter but also advances our understanding of topochemical reaction processes in extended solids.

Strain-Induced Anion-Site Occupancy in Perovskite Oxyfluoride Films

“…Synthesis of heterostructures and thin films also allows for strain engineering, which may alter anion-site occupation in heteroanionic materials. For instance, experimental and computational studies have revealed that strain can alter preferred lattice positions of different anions in oxynitrides, oxyhydrides, and oxysulfides. − However, we are unaware of experimental work demonstrating the use of substrate-induced strain to alter or direct the F incorporation.…”

Strain-Assisted Topochemical Synthesis of La-Doped SrVO2H Films

“…The substrate employed appears critical for hydride introduction because when a (La 0.3 Sr 0.7 ) (Al 0.65 Ta 0.35 )O 3 (LSAT) substrate is used for x = 0, an oxygen-depleted phase results. 4,28 As can be seen in Figure 4d, the evolution of the cell parameters as a function of x is highly anisotropic, that is, a is nearly unchanged while c increases linearly. It is remarkable that the volume change in the oxyhydride films with x is much steeper than that of the parent Sr 1−x La x VO 3 solid solution (Figure 4h).…”

High-Pressure and High-Temperature Synthesis of Anion-Disordered Vanadium Perovskite Oxyhydrides

“…The first-principles calculation revealed that the trans -preference caused by the characteristic crystal field splitting as well as a coherent shrinkage along the V–H–V direction due to anion ordering stabilizes the ordered structure . In fact, tensile strain in the thin film sample induces the anion disordering, suggesting that the lattice parameters are strongly connected with the order–disorder phenomena …”

“…28 In fact, tensile strain in the thin film sample induces the anion disordering, suggesting that the lattice parameters are strongly connected with the order−disorder phenomena. 29 Herein, we report anion-disordered perovskite Sr 1−x Na x VO 3−y H y (x = 0, 0.05, 0.1, 0.2). High-pressure and high-temperature synthesis from nominal composition SrVO 2 H yielded anion-disordered SrVO 3−y H y (y ∼ 0.4) with a significant amount of byproducts, while Na substitution resulted in an almost pure anion-disordered phase of Sr 1−x Na x VO 3−y H y with an increased amount of hydride anions (y ∼ 0.7 for x = 0.2).…”