Magnetically Manipulable Ionic Liquid Crystals Incorporating Neutral Radicals.

Invited for this month's cover are the collaborating groups of Dr. Yoshiaki Uchida from Osaka University, Japan, Prof. Rui Tamura and Prof. Masahito Sugiyama from Kyoto University, Japan and Dr. Dmitrii G. Mazhukin from Novosibirsk State University, Russia. The cover picture depicts a contrast between localized spins and conductive ions in the newly-synthesized ionic liquid crystalline (ILC) nitroxide radicals. The ILC droplet of the new compounds is magnetically manipulable. More information can be found in the Full Paper by Yoshiaki Uchida, Rui Tamura, and co-workers.

Magnetically Manipulable Ionic Liquid Crystals Incorporating Neutral Radical Moiety.

With a view to fabricating a new remote input-output system by applying functional ionic liquid crystalline (ILC) materials, we have developed novel ILC compounds containing a nitroxide radical unit in the organic cations, which show an enantiotropic smectic A (SmA) phase. We have implemented the magnetic manipulation of a droplet of one of the ILC compounds on the basis of the intermolecular magnetic interactions between radical moieties. This ILC monoradical compound shows a 55 % larger increase in paramagnetic susceptibility at the solid-to-LC melting point in the first heating process than the non-ionic LC monoradical compounds. It is most likely owing to the nanosegregation of strongly bonded ionic and non-ionic moieties. The increased molar magnetic susceptibility is preserved not only in the SmA phase but also in the isotropic liquid and solid phases during the first cooling process.

Oxyhydrides of (Ca,Sr,Ba)TiO3 perovskite solid solutions.

The oxyhydride solid solutions (Ca,Sr)TiO(3-x)H(x) and (Sr,Ba)TiO(3-x)H(x) have been prepared by reducing the corresponding ATiO(3) oxides with calcium hydride. Under the reaction conditions examined, a hydride content of x = 0.1-0.3 was obtained for all compositions. Compared to our previous result with BaTiO(3-x)H(x), the larger particle size in this study (20-30 µm vs 170 nm) resulted in a somewhat lower hydride amount despite prolonged reaction times. We examined changes in cell volume, octahedral tilt angle, and site occupancy of different anion sites after conversion to oxyhydrides; it appears that these oxyhydrides fit the geometrical descriptions typical for regular ABO(3) perovskites quite well. The hydrogen release temperature, previously shown to be indicative of the hydride exchange temperature, however, does not scale linearly with the A-site composition, indicating a potential effect of chemical randomness.

Epitaxial thin films of ATiO(3-x)H(x) (A = Ba, Sr, Ca) with metallic conductivity.

Epitaxial thin films of titanium perovskite oxyhydride ATiO(3-x)H(x) (A = Ba, Sr, Ca) were prepared by CaH(2) reduction of epitaxial ATiO(3) thin films deposited on a (LaAlO(3))(0.3)(SrAl(0.5)Ta(0.5)O(3))(0.7) substrate. Secondary ion mass spectroscopy detected a substantial amount and uniform distribution of hydride within the film. SrTiO(3)/LSAT thin film hydridized at 530 °C for 1 day had hydride concentration of 4.0 × 10(21) atoms/cm(3) (i.e., SrTiO(2.75)H(0.25)). The electric resistivity of all the ATiO(3-x)H(x) films exhibited metallic (positive) temperature dependence, as opposed to negative as in BaTiO(3-x)H(x) powder, revealing that ATiO(3-x)H(x) are intrinsically metallic, with high conductivity of 10(2)-10(4) S/cm. Treatment with D(2) gas results in hydride/deuteride exchange of the films; these films should be valuable in further studies on hydride diffusion kinetics. Combined with the materials' inherent high electronic conductivity, new mixed electron/hydride ion conductors may also be possible.

An oxyhydride of BaTiO3 exhibiting hydride exchange and electronic conductivity.

In oxides, the substitution of non-oxide anions (F(-),S(2-),N(3-) and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H(-)) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO(3), as an O(2-)/H(-) solid solution with hydride concentrations up to 20% of the anion sites. BaTiO(3-x)H(x) is electronically conducting, and stable in air and water at ambient conditions. Furthermore, the hydride species is exchangeable with hydrogen gas at 400 °C. Such an exchange implies diffusion of hydride, and interesting diffusion mechanisms specific to hydrogen may be at play. Moreover, such a labile anion in an oxide framework should be useful in further expanding the mixed-anion chemistry of the solid state.