We describe the fabrication of crystalline electrically conducting antimony-doped tin oxide (ATO) nanoparticles highly dispersible in polar solvents such as water and ethanol without any stabilizing agents. Nonagglomerated monodisperse ATO nanoparticles with different doping levels are obtained by a facile solvothermal reaction in tert-butanol, leading to the formation of monodisperse nanocrystals with a size of about 3 nm directly after synthesis. Electrical conductivity of ATO nanoparticles strongly increases due to the substitutional doping with antimony, reaching 6.8 × 10 −2 S cm −1 for the as-synthesized nanoparticles prepared with 3−5 mol % Sb. This increase stems from transition from hopping in the undoped samples to band-like conduction in the doped samples as revealed by terahertz (THz) spectroscopy measurements describing transport on nanometer distances. The dc conductivity of the doped nanoparticles increases by about 3 orders of magnitude up to 62 S cm −1 after annealing in air at 500°C. The electrical conductivity, crystallinity, small size, and high dispersibility in polar solvents make the obtained ATO nanoparticles promising building blocks for the direct assembly of more complex conducting architectures using polymer templates that could be damaged in organic solvents. We illustrate the benefits of the water-dispersible ATO nanoparticles by their assembly to periodic macroporous electrodes using poly(methyl methacrylate) (PMMA) beads as the porosity templates. Aqueous dispersion of ATO nanoparticles can be directly combined with PMMA beads that are easily removed by calcination, enabling a facile deposition of 3D-macroporous ATO electrodes featuring optical transparency and a large periodically ordered conducting interface.T ransparent conducting oxides (TCOs) combine transparency in the visible range with high electrical conductivity, which makes them important materials for numerous optoelectronic and optoelectrochemical applications. TCOs are predominantly produced as thin dense layers, but the recent years are marked by a fast-growing interest in other types of TCO architectures motivated by the development of novel applications. Particularly, nanoparticles are one of intensively studied TCO morphologies. The colloidal dispersions of TCO nanoparticles are of significant interest for wet chemical deposition and printing of conducting crystalline coatings, 1−4 with expected benefits of decreased processing costs, the possibility of coating temperature-sensitive substrates, or surface patterning. Furthermore, the TCO nanoparticles gain importance as building blocks for the assembly of porous electrode architectures. 5−10 Due to their practical relevance, nanoparticles of different TCO materials such as indium tin oxide (ITO), antimony doped tin oxide (ATO), and aluminum doped zinc oxide (AZO) are already available commercially. 11 Furthermore, TCO nanoparticles have been synthesized by various methods such as coprecipitation, 12−17 hydrothermal, 18−22 solvothermal, 17,23−31 sol−gel 32,33 and mi...

Infrared reflectivity spectra of cubic SrMnO 3 ceramics reveal 18% stiffening of the lowest-frequency phonon below the antiferromagnetic phase transition occurring at T N = 233 K. Such a large temperature change of the polar phonon frequency is extraordinary and we attribute it to an exceptionally strong spin-phonon coupling in this material. This is consistent with our prediction from first-principles calculations. Moreover, polar phonons become Raman active below T N , although their activation is forbidden by symmetry in the P m3m space group. This gives evidence that the cubic P m3m symmetry is locally broken below T N due to a strong magnetoelectric coupling. Multiphonon and multimagnon scattering is also observed in Raman spectra. Microwave and THz permittivity is strongly influenced by hopping electronic conductivity, which is caused by small nonstoichiometry of the sample. Thermoelectric measurements show room-temperature concentration of free carriers n e = 3.6 × 10 20 cm −3 and the sample composition Sr 2+ Mn 4+ 0.98 Mn 3+ 0.02 O 2− 2.99 . The conductivity exhibits very unusual temperature behavior: THz conductivity increases on cooling, while the static conductivity markedly decreases on cooling. We attribute this to different conductivity of the ceramic grains and grain boundaries.

We studied THz dielectric spectra of SrTiO 3 / DyScO 3 epitaxial multilayers with four 50-nm-thick layers of each compound deposited on DyScO 3 substrate as a function of temperature and electric field. At room temperature, SrTiO 3 is in the paraelectric phase and, due to the in-plane tensile strain within the films, the soft-mode frequency is shifted down to 47 cm −1 . The ferroelectric phase transition occurs in the strained SrTiO 3 layers around 270 K and in the ferroelectric phase the soft-mode hardening upon temperature decrease is observed. The soft mode is linearly coupled to an excitation of relaxation type at 10 cm −1 at all temperatures. This relaxation is silent in the paraelectric phase, but it becomes coupled to the polarization below the ferroelectric transition temperature and its strength progressively increases. The recently proposed universal model of soft-mode behavior in strained SrTiO 3 films ͓C. Kadlec et al., J. Phys.: Condens. Matter 21, 115902 ͑2009͔͒ was generalized to describe the observed spectra at all temperatures and applied fields.