SrTiO3 undergoes a cubic-to-tetragonal phase transition at 105K. This antiferrodistortive transition is believed to be in competition with incipient ferroelectricity. Substituting strontium by isovalent calcium induces a ferroelectric order. Introducing mobile electrons to the system by chemical non-isovalent doping, on the other hand, leads to the emergence of a dilute metal with a superconducting ground state. The link between superconductivity and the other two instabilities is a question gathering momentum in the context of a popular paradigm linking unconventional superconductors and quantum critical points. We present a set of specific-heat, neutronscattering,dielectric permittivity and polarization measurements on Sr1−xCaxTiO3 (0 < x < 0.009) and a study of low-temperature electric conductivity in Sr0.9978Ca0.0022TiO 3−δ . Calcium substitution was found to enhance the transition temperature for both anti-ferrodistortive and ferroelectric transitions. Moreover, we find that Sr0.9978Ca0.0022TiO 3−δ has a superconducting ground state. The critical temperature in this rare case of a superconductor with a ferroelectric parent, is slightly lower than in SrTiO 3−δ of comparable carrier concentration. A three-dimensional phase diagram for Sr1−xCaxTiO 3−δ tracking the three transition temperatures as a function of x and δ results from this study, in which ferroelectric and superconducting ground states are not immediate neighbours.

This work reports the development of atmospheric pressure plasma reactor with dielectric barrier discharge DBD for material treatment. The DBD discharge has been generated in planar geometry reactor powered by ac voltage provided by conventional high voltage transformer. The dielectric barrier consisted of two glass slabs, which cover both reactor electrodes. The air discharge gap between the dielectric layers was varied from 1.0 to 3.0mm. The power consumption of the DBD reactor was evaluated by the Lissajous figures method. The optimization of reactor geometry for material processing is discussed.

Transport properties and magnetization measurements of the K x MoO 2−␦ ͑0 Յ x Յ 0.25͒ compound are reported. The compound crystallizes in the oxygen deficient MoO 2 monoclinic structure with potassium atoms occupying interstitial positions. An unconventional metallic behavior with power-law temperature dependence is related to a magnetic ordering. Superconducting transition with small volume fraction is also observed near 7 K for a sample with low potassium composition.

Coexistence between superconductivity and magnetism is reported for the KxMoO2−δ samples. Photoemission experiments show that the presence of Mo3+ ions is responsible for the weak ferromagnetic ordering observed in the KxMoO2−δ samples. Magnetic ordering temperature and superconducting critical temperature (TC) ratio range from 7 to 18 in this compound. These are the highest ratios reported so far for a magnetic superconductor. TC decreases with increasing potassium composition (x). For the first time, TC near 10 K is reported in the K-Mo-O system.

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K 0.05 MoO 2 has been studied by x-ray and neutron diffractometry, electrical resistivity, magnetization, heat capacity, and thermal expansion measurements. The compound displays two phase transitions, a first-order phase transition near room temperature and a second-order transition near 54 K. Below the transition at 54 K, a weak magnetic anomaly is observed and the electrical resistivity is well described by a power-law temperature dependence with exponent near 0.5. The phase transitions in the K-doped MoO 2 compound have been discussed for the first time using neutron diffraction, high resolution thermal expansion, and heat capacity measurements as a function of temperature. V

In this work, structural and physical properties are revisited in the MoO 2 compound. MoO 2 single crystals have been prepared by chemical vapor transport technique and characterized by X-ray diffraction, neutron diffraction, high-resolution thermal expansion, electrical resistance measurements, and heat capacity. Electrical resistivity, heat capacity, and thermal expansion measurements show two clear features which are related to a phase transitions on the MoO 2 compound. These results suggest that an electronic-type transition occurs near 220 K and a structural transition at ~ 267 K.

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