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Thermal diffusivity and thermal conductivity of single crystals of Nd3+ doped GdVO4, YVO4, LuVO4, and Y3Al5O12 are precisely measured over a wide range of doping concentration from 0.5 to 15 at. % by temperature wave analysis. Thermal diffusivity serves as the most sensitive parameter to detect the effect of doping on thermal properties, where Nd3+ doped GdVO4 exhibits a decrease in thermal diffusivity (it has changed about 20% in their values in the c axis) but an increase in heat capacity (only 1.7%). It has long been understood that the thermal conductivity of YVO4 is inferior to that of Y3Al5O12; however, the thermal conductivity of YVO4 in the c axis shows the highest value in all four crystals compared at 1 at. % of Nd3+ doping concentration. Thermal conductivity exhibits a decrease (∝[variant_greek_epsilon]-1/2, [variant_greek_epsilon]: mass variance) with an increase of doping concentration, that is characteristic of Klemens’ point defect model for the phonon scattering. In the numerical fitting, the anisotropic decrease of thermal conductivity in different crystal axes, [100], [001], and [110], is reflected as the different phonon velocities. The simulated and the experimental thermal conductivity show the various decreasing curvatures indicating that the effect of mass difference of the host and the doping cations serves as an important factor, as with the crystallographic anisotropy, on the thermal conductivity of the doped single crystals. [ABSTRACT FROM AUTHOR]

A study was conducted to measure the thermal diffusivity, heat capacity, and thermal conductivity of single crystals of [Nd.sup.3+] doped GdV[O.sub.4], YV[O.sub.4], LuV[O.sub.4], and [Y.sub.3][Al.sub.5][O.sub.12]. The results revealed that both the crystallographic anisotropy and the mass difference of the host and the doping cations play significant role for the doping effect on the thermal conductivity of laser crystals.

A new polymorph of BaCN2 was obtained via a simple nitridation reaction of BaCO3 under an NH3 flow at 900 °C. The product was analyzed via single crystal X-ray diffraction and infrared spectroscopy, and it was found to have a tetragonal I4/mcm crystal structure (space group no. 140) with a = 0.60249(4) nm and c = 0.71924(5) nm. In this structure, each Ba2+ cation is situated in the square antiprism of N atoms of NCN2− anionic groups. Eu2+ doped BaCN2 can be excited by irradiation of blue and green light (from 400 to 550 nm), and it generates an intense red emission peak at 660 nm with a quantum efficiency of 42% in response to 465 nm excitation at room temperature. The peak emission wavelength varies over an extremely wide range of temperature, from 640 nm at 500 K to 680 nm at 80 K, and this red-shift with decreasing temperature is attributed to a unit cell shrinkage that results in significant crystal field splitting of the 5d energy levels of the Eu2+ ions. [ABSTRACT FROM AUTHOR]

Indium oxychalcogenides would be attractive semiconductors considering the practical use of indium oxides and sulfides such as indium–tin oxides (ITO) and copper–indium–gallium diselenides (CIGS). In this work, a novel layered indium oxysulfide, LaOInS2, was synthesized by a metathesis reaction between LaOCl and NaInS2. Synchrotron X-ray diffraction showed that LaOInS2 consisted of alternately stacked rocksalt-type In–S and PbO-type La–O layers. The InS6 octahedron had split In sites with abnormally large anisotropic atomic displacement factors. LaOInS2 was found to be a direct semiconductor. Density functional theory calculations exhibited well-dispersed bands composed of In 5s/5p and S 3p/O 2p orbitals with a band gap of ∼2.4 eV, which was close to the experimental value estimated by optical absorption (2.64 eV). Under visible light irradiation this visible-light absorption, LaOInS2 exhibited photocatalytic activity for H2 and O2 evolution from water with the aid of Pt and IrO2 cocatalysts, respectively. [ABSTRACT FROM AUTHOR]

Metastable c-Al xT1− xN is an important and well-established hard coating in the tool industry. To improve the mechanical and thermal properties, Al-rich c-Al xTi1− xN coatings with controllable preferred crystal orientations were fabricated via low-pressure chemical vapor deposition ( LP- CVD) in an industrial plant, using an AlCl3-TiCl4-NH3-Ar-H2 precursor system. The c-Al xTi1− xN coatings with (100)- and (111)-preferred orientations and average x values of 0.82 and 0.73, respectively, comprised c-Al(Ti)N/c-Ti(Al)N nanolamellae with average compositions of c-Al0.9Ti0.1N/c-Al0.6Ti0.4N and c-Al0.80Ti0.20N/c-Al0.50Ti0.50N; the average lamellar periods were 7.7 and 4.5 nm, respectively. High-resolution transmission electron microscopy indicated that the c-Al(Ti)N/c-Ti(Al)N nanolamellae were modulated along the <100> direction, implying coherent spinodal decomposition of c-Al xTi1− xN in the as-deposited state. The hardness of the c-Al xTi1− xN coatings varied from 33 to 36 GPa, depending on the (100)- or (111)-preferred orientation. Residual stress measurements in the as-deposited state showed tensile stress values of 1.8 and 4.6 GPa for the (100)- and (111)-oriented c-Al xT1− xN coatings, respectively. This stress may be generated by the difference in the thermal expansion coefficient of the c-Al xT1− xN coating and the carbide substrate and by coherency stress in the c-Al(Ti)N/c-Ti(Al)N nanolamellae. In situ high-temperature X-Ray diffraction results revealed high thermal stability up to 1000°C. [ABSTRACT FROM AUTHOR]

Lithium ion conductors with garnet-type structure are promising candidates for applications in all solid-state lithium ion batteries, because these materials present a high chemical stability against Li metal and a rather high Li+ conductivity (10−3-10−4 S/cm). Producing densified Li-ion conductors by lowering sintering temperature is an important issue, which can achieve high Li conductivity in garnet oxide by preventing the evaporation of lithium and a good Li-ion conduction in grain boundary between garnet oxides. In this study, we concentrate on the use of sintering additives to enhance densification and microstructure of Li7La3ZrNbO12 at sintering temperature of 900°C. Glasses in the LiO2-B2O3-SiO2-CaO-Al2O3 ( LBSCA) and BaO-B2O3-SiO2-CaO-Al2O3 ( BBSCA) system with low softening temperature (<700°C) were used to modify the grain-boundary resistance during sintering process. Lithium compounds with low melting point (<850°C) such as LiF, Li2 CO3, and Li OH were also studied to improve the rearrangement of grains during the initial and middle stages of sintering. Among these sintering additives, LBSCA and BBSCA were proved to be better sintering additives at reducing the porosity of the pellets and improving connectivity between the grains. Glass additives produced relative densities of 85-92%, whereas those of lithium compounds were 62-77%. Li7La3ZrNbO12 sintered with 4 wt% of LBSCA at 900°C for 10 h achieved a rather high relative density of 85% and total Li-ion conductivity of 0.8 × 10−4 S/cm at room temperature (30°C). [ABSTRACT FROM AUTHOR]

Simultaneous effect of AlO and LiBO additions on sintering behavior and Li-ion conductivity of LiLaCaZrTaO (LLCZT) garnet electrolyte sintered at 900°C (10 h) is evaluated. The crystal phase and microstructure of the different composites were evaluated by x-ray diffraction and scanning electron microscopy (SEM), respectively. Electrical properties of the composites with high relative densities (95%) were examined by impedance spectroscopy. The cubic phase was formed for LLCZT sintered with 0-0.21 mol of AlO and 0.70 mol-0.80 mol of LiBO. The excess of AlO (0.22 mol) led to the formation of secondary phases. SEM observation revealed the good interconnection between LLCZT grains and the distribution of the glassy phase formed by LiBO and AlO. Effective combination of 0.21 mol of AlO and 0.80 mol of LiBO produced denser material with high relative density of 95% and high Li-ion conduction of 1 × 10 S/cm at 32°C. [ABSTRACT FROM AUTHOR]