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The near-infrared luminescence properties of the nanoscale erbium ceramic cluster (THF)14Er10S6Se12I6 (Er10, where THF = tetrahydrofuran) and the molecular erbium thiolate (DME)2Er(SC6F5)3 (Er1, where DME = 1,2-dimethoxyethane) were studied by optical absorption, photoluminescence, and vibrational spectroscopy. The calculated radiative decay time of 4 ms for the ⁴I13/2 → ⁴I15/2 transition is comparable to the reported values for previously reported organic complexes. The recorded emission spectrum of the ⁴I13/2 → ⁴I15/2 transition was centered at 1544 nm with a bandwidth of 61 and 104 nm for Er10 and Er1, respectively, with stimulated emission cross sections of 1.3 × 10^-20 cm² (Er10) and 0.8 × 10^-20 cm² (Er1) that are comparable to those of solid-state inorganic systems. Lifetime measurements of the 1544 nm decay showed a fluorescence decay time of the order of 3 ms for Er10 that, together with the radiative decay time, yielded a quantum efficiency above 78%, which is considered to be the highest reported value for a “molecular” erbium compound. This efficiency is attributed to the absence of direct Er coordination with fluorescence quenching vibrational groups such as hydrocarbon and bonding of hydroxide groups. The direct coordination of S, Se, and I accounts for the improved fluorescence spectral properties. These properties result because these anions are heavy and form stable but weak bonds to facilitate a low phonon energy host environment for the erbium.

We demonstrated the formation of single-crystal-like materials that contain preferentially oriented arrays of lead zirconate titanate (PZT) cube-shaped particles by self-assembly. Hydrothermally synthesized PZT particles with a bulk composition of Zr/Ti = 70/30 were used in making microcrystal arrays. Spreading a suspension containing PZT cube-shaped particles, 2-propanol, and mineral oil at the air−water interface produced a one-dimensional planar array of PZT particles on the water surface. The array so formed was subsequently transferred onto a flat or curved substrate. X-ray diffraction and electron backscattered diffraction analyses revealed that most of the cube-shaped particles in the array were oriented with their pseudocubic 〈001〉 direction aligned parallel to the normal direction of the substrate surface. Filling the arrays with matrixes produced monolayer or multilayer textured composites. The piezoelectric properties of oriented cube-shaped micron-sized particles in the self-assembled arrays were measured using a modified atomic force microscope to reveal the ferroelectric nature of the PZT arrays.

Amorphous Zr−Ti hydrous oxide submicrometer spheres were employed in hydrothermal syntheses of PbZr0.7Ti0.3O3 heteroepitaxial thin films on single-crystal SrTiO3 substrates. Reactions utilizing processing variables that included precursor concentration (0.1−0.4 m), KOH concentration (6−12 m), and time (24−60 h) were carried out at 150 °C to evaluate the effect of this precursor on the formation of an epitaxial film. Selected experiments were also conducted to examine how this spherical precursor compares with two other precursor systems, that is, nanostructured amorphous Zr−Ti hydrous oxide prepared by coprecipitation at room temperature, and a mixture of crystalline TiO2 and amorphous ZrO2·nH2O obtained from soluble ZrOCl2·8H2O. On the basis of the results of X-ray diffraction and electron microscopy, precursor choice, precursor concentration, and KOH mineralizer concentration have a significant effect on the quality, composition, and morphology of the film.

A thermodynamic model of electrolyte solutions has been used as a tool for equilibrium calculations in the Na−Bi−Ti−H2O and K−Bi−Ti−H2O systems. To perform the calculations, unknown standard-state properties for Na0.5Bi0.5TiO3 (NBT), K0.5Bi0.5TiO3 (KBT) and other solid compounds that exist in these systems were established. As a result of the calculations, stability and yield diagrams of the investigated systems were computed. Thus, the optimum conditions (i.e., temperature, synthesis precursor concentrations, solution pH) for the hydrothermal synthesis of phase-pure KBT and NBT are presented in a graphical form. They show the concentrations of precursors and pH-adjusting agents required for the formation of phase-pure alkaline bismuth titanates. The computed diagrams show that the formation of phase-pure sodium and potassium bismuth titanates takes place in highly alkaline solutions (e.g., at pH above 11.4 and 12.2, respectively, at 473 K). Results of our experiments validated the newly developed yield diagrams and demonstrated, for the first time, that alkaline bismuth titanates can be hydrothermally synthesized. Experimental synthesis was carried out using both conventional and microwave-heated reactors.

A comprehensive thermodynamic model has been applied to predict the optimum conditions for the hydrothermal synthesis of phase-pure strontium zirconate. The model is based on the accurate knowledge of standard-state thermochemical properties of all species and a realistic activity coefficient model. The predictions are conveniently summarized in the form of phase stability and yield diagrams. Unlike our previous works, the diagrams are automatically generated using newly developed software, which makes it possible to analyze the effect of reactant identity and concentrations, contaminants, pH, and temperature as independent variables. The calculations revealed a high sensitivity of the synthesis to the identity of Sr precursors, Sr/Zr molar ratio of starting materials, and temperature as well as to the contamination with carbonates. The predictions have been confirmed experimentally at two temperatures (433 and 473 K) using strontium hydroxide or strontium nitrate as sources of Sr and a hydrous zirconium dioxide as a source of Zr. Both the predictions and experiment demonstrate that phase-pure SrZrO3 can be obtained only when all starting materials are CO2-free.