ChemInform Abstract: An Antiferro‐to‐Ferromagnetic Transition in EuTiO_3‐xH_x Induced by Hydride Substitution.

Abstract

Substitution. -EuTiO 3-xHx (x  0.3) is prepared by low temperature CaH2 reduction of Eu 2Ti2O7 and EuTiO3 (475-650 C, 2 d) and characterized by XRD and magnetic measurements. The samples crystallize with the ideal perovskite structure in the cubic space group Pm3m, where O/H anions are randomly distributed. EuTiO3-xHx shows metallic resistivity and an antiferromagnetic-to-ferromagnetic transition at the Curie temperature of 12 K. The Curie temperature of EuTiO 3-xHx is higher than that of any other EuTiO3-derived ferromagnet. -(YAMAMOTO, T.; YOSHII, R.; BOUILLY, G.; KOBAYASHI, Y.; FUJITA, K.; KUSUSE, Y.; MATSUSHITA, Y.; TANAKA, K.; KAGEYAMA*, H.; Inorg. Chem. 54 (2015) 4, 1501-1507, http://dx.doi.org/10.1021/ic502486e ; Dep. Energy Hydrocarbon Chem., Grad. Sch. Eng., Kyoto Univ., Nishikyo, Kyoto 615, Japan; Eng.) -W. Pewestorf 17-010

Selective Hydride Occupation in BaVO3–xHx (0.3 ≤ x ≤ 0.8) with Face- and Corner-Shared Octahedra

“…The bond valence sum (BVS) value for V is +2.7, which is similar to that of h-BVOH8 as shown later. The calculated density of c-BVOH9, 5.77 g/cm 3 , is higher than 5.69 g/cm 3 for the almost isocompositional h-BVOH8, justifying the formation (and stabilization) of the former under higher pressure. Similar hexagonal-to-cubic perovskite transitions by pressurization were reported previously in oxides.…”

Promoted Hydride/Oxide Exchange in SrTiO3 by Introduction of Anion Vacancy via Aliovalent Cation Substitution

“…Among polycrystalline samples of ATiO 3−x H x , the maximum hydrogen incorporation has been achieved for A = Ba, where the oxygen site can be substituted up to x = 0.6, while the substitution limits for other A look much smaller (x ≤ 0.3 for Sr and Eu and 0.1 for Ca). 2,3 The reason could be related to the more electropositive nature of Ba, a factor which may stabilize H 1s orbitals and increase the solubility range. Alternatively, the larger lattice for Ba may facilitate anion diffusion to assist the hydride/oxide exchange.…”

“…9,10 Metallic EuTiO 3−x H x undergoes a ferromagnetic transition at 12 K, which is much higher than those of cationsubstituted oxides. 3 Furthermore, hydride exchange reactions using titanium oxyhydrides as precursors have been developed; the labile nature of hydride anion allows access to various mixed-anion oxides. Oxynitrides ATiO 3−x N 2x/3 result when oxyhydrides ATiO 3−x H x are heated under NH 3 11 or even N 2 12 gas at around 400 °C.…”

Pressure-Stabilized Cubic Perovskite Oxyhydride BaScO2H

“…4 A cation/anion cosubstituted perovskite SrCr 3+ O 2 H with respect to the isoelectronic RCr 3+ O 3 (R = rare earths) offers a new pathway to extensively tune tolerance factor t, leading to a higher Neél temperature for SrCrO 2 H (t ∼ 1) than for any Cr(III) oxides. 9 Second, excellent electric conductivity as well as thermal stability in ATi(O,H) 3 (A = Ca, Sr, Ba, and Eu), 8,13 possibly related to hydride's adjustability to fit its size with oxide anion, ensure potential applications for a wide range of electronic devices. Finally, the labile nature of hydride in BaTi(O,H) 3 provides new multistep topochemical routes to access mixed anion compounds such as BaTi(O,N) 3 with ferroelectricity 14 and BaTi(O,H,OH) 3 with unprecedented coexistence of H − and H + .…”