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Perovskite-type oxides have proven to be a versatile class of compounds with systematic study of their structure and various properties. Further structural variations and properties can be added by adding a second anionic species other than oxide, such as hydride, fluoride, nitride, or others. The different charge, covalency, size, and new modes of local coordination offer convenient ways to further control carrier doping, magnetism, conductivity, and even chemical reactivity. In this review we examine the recent work concerning various mixed-anion perovskites and conclude with potential new directions for the further development of these materials. [ABSTRACT FROM AUTHOR]

In this review we describe recent advances in transition metal oxyhydride chemistry obtained by topochemical routes, such as low temperature reduction with metal hydrides, or high-pressure solid-state reactions. Besides the crystal chemistry, magnetic and transport properties of the bulk powder and epitaxial thin film samples, the remarkable lability of the hydride anion is particularly highlighted as a new strategy to discover unprecedented mixed anion materials. [ABSTRACT FROM AUTHOR]

The high-pressure synthesis of a manganese oxyhydride LaSrMnO3.3H0.7 is reported. Neutron and X-ray Rietveld analyses showed that this compound adopts the K2NiF4 structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO4 that result in only oxygen-deficient phases down to LaSrMnO3.5. This suggests that high H2 pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition-metal oxyhydrides. Magnetic susceptibility revealed a spin-glass transition at 24 K that is due to competing ferromagnetic (Mn2+-Mn3+) and antiferromagnetic (Mn2+-Mn2, Mn3+-Mn3+) interactions. [ABSTRACT FROM AUTHOR]

We report a novel oxyhydride SrCrO2H directly synthesized by a high-pressure high-temperature method. Powder neutron and synchrotron X-ray diffraction revealed that this compound adopts the ideal cubic perovskite structure (Pm3m) with O2-/H- disorder. Surprisingly, despite the nonbonding nature between Cr 3d t2g orbitals and the H 1s orbital, it exhibits G-type spin ordering at TN≈380 K, which is higher than that of RCrO3 (R=rare earth) and any chromium oxides. The enhanced TN in SrCrO2H with four Cr-O-Cr bonds in comparison with RCr3+O3 with six Cr-O-Cr bonds is reasonably explained by the tolerance factor. The present result offers an effective strategy to tune octahedral tilting in perovskites and to improve physical and chemical properties through mixed anion chemistry. [ABSTRACT FROM AUTHOR]

We investigate the low temperature anion exchange behavior of hydride and oxide in perovskite oxynitrides. CaH 2 reduction of (Sr 1– x La x )Ti(O 3 –x N x ) (0< x ≤ 1) resulted in the selective anion exchange of hydride for oxide rather than nitride, yielding the oxyhydride-nitride (Sr 1– x La x )Ti(O 3 –x–y H y N x ). However, the exchange of hydride is drastically suppressed with increasing nitrogen content and is completely impeded when the nitride content reaches 10% of the anionic site. This implies that the N 3– anions in the oxide lattice play a crucial role in lowering diffusion of O 2– (and H – ). The present study indicates the necessity to consider kinetic aspects when manipulating anion compositions, in particular in a mixed anion system with a small amount of anion vacancies. [ABSTRACT FROM AUTHOR]