Temperature driven reactant solubilization synthesis of BiCuOSe.

Phase-pure BiCuOSe, which is isostructural to the layered p-type transparent conductor LaCuOS, has been synthesized in high yield by a single-step hydrothermal reaction at low temperature (250 degrees C) and pressure (<20 atm). A moderate reaction temperature of 250 degrees C was sufficiently high to solubilize both Bi2O3 and Cu2O and stabilize monovalent copper and low enough to impede the oxidation of dianionic selenium. BiCuOSe exhibits a relatively high electrical conductivity (sigma approximately 3.3 S cm(-1)) and a reduced band gap (E(g) = 0.75 eV), which compare favorably with the optoelectronic properties of BiCuOS and the cerium-based oxysulfides, CeAgOS and CeCuOS.

Silver delafossite oxides.

A single-step, low-temperature (<210 degrees C) and -pressure (<20 atm) hydrothermal method has been developed to synthesize a series of silver delafossites, AgBO2 (B = Al, Ga, Sc, and In). Experimental and computational studies were performed to understand the optical and electric properties of these silver delafossites, including the first in-depth study of AgAlO2 and AgScO2. Their properties were examined as a function of the trivalent cation radius and compared to those of copper delafossites to elucidate the role of both the A- and B-site cations. While optical band gaps for silver delafossites were larger and visible light absorption was lower than values previously reported for polycrystalline powder samples of copper delafossites, the conductivities of silver delafossites are similar or lower. Electronic structure calculations indicate that these properties are due to the scarcity of silver 4d states just below the valence band maximum.

Facile synthesis of BiCuOS by hydrothermal methods.

BiCuOS, which is isostructural to the layered rare-earth oxysulfides LnCuOS (Ln = La-Eu), was synthesized by a single-step hydrothermal reaction at low temperature (250 degrees C) and pressure (<20 atm). Particular emphasis is placed on how the selection of the proper reaction conditions, such as temperature and pH, achieves a mutual high solubility of the metal-oxide reactants, Bi2O3 and Cu2O, and thus generates BiCuOS in a good yield. The optical and electrical properties of BiCuOS were measured to determine the influence of replacing a rare-earth cation with bismuth. The electrical conductivity of BiCuOS is increased over that of certain layered rare-earth oxysulfides, LnCuOS (Ln = La, Pr, and Nd), and is similar to that of the cerium members, CeCuOS and CeAgOS. Band structure calculations reveal that, similar to other potential transparent conductors containing sixth-row elements, relativistic effects significantly lower the energy of the conduction band, and thus narrow the optical band gap. These low-energy conduction bands are responsible for the electrical and optical properties of BiCuOS.