Thin films of Wo3 deposited on quartz substrates at room temperature have been shown to be amorphous in structure. The optical absorption spectra of the amorphous and crystalline films have been measured in the temperature range 110° to 500°K. The fundamental absorption edge of an amorphous film occurs at 3800 A which on crystallization moves to 4500 A. On the high-energy side of the absorption edge several absorption peaks are resolvable in both types of film. The frequency dependence of the absorption coefficient below 104 cm−1 is described by an expression of the form K (v, T) = K 0 exp[− (β/kT) (E 0 − hv)] and above 104 cm−1 it follows a square law dependency. The temperature coefficient of the band edges was found to be − 5.0 × 10−4 eV/°K and the estimated band gaps at 0°K were found to be 3.65 and 3.27 eV for the amorphous and crystalline films, respectively. The electrical conductivity of a thin film has been measured in the temperature range 298–573°K and the activation energy was found t...

Optical and photoelectric properties and colour centres in thin films of tungsten oxide

The Binary Rare Earth Oxides.

Publisher Summary The physical properties given in this compilation are listed in the accompanying tabulation according to the table given in this chapter in which they can be found. Values for two quantities that have frequently been used in alloying theory studies, viz., the metallic radius and electronegativity, are not included here. Other properties, such as magnetic susceptibility, electrical resistivity, and thermal conductivity, which are generally of interest to those studying solids, are not included in this compilation primarily because such properties do not appear to be important in alloying theory. The derived properties and some interrelationships of the physical properties are examined and discussed in this chapter. Those subjects which also appear in tabulated form are listed in the accompanying tabulation. The initial goal in our alloy-theory program was a set of Gruneisen constants and a set of size factors. To calculate these quantities, almost all of the physical properties given herein are needed in the computations. Some of the other derived quantities are not only intermediate steps in the computations of the Gruneisen constant and size factor, but also serve as checks on the consistency of initial data (i.e., the measured physical properties of the elements). Some of the “constants” of the elements—that is, the Griineisen constant, entropy of fusion, etc., which have been derived for a few elements and then generally assumed to apply to all elements—are examined to see if this generalization is valid.

Physical Properties and Interrelationships of Metallic and Semimetallic Elements

Values for standard enthalpies of formation and dissociation energies for gaseous diatomic monoxides have been selected by critical assessment of experimental data from the literature. Gibbs energy functions, (−(G○T −H○298)/T), and enthalpy functions, (H○T −H○298), have been calculated from literature values for molecular parameters. Computer methods of storage, processing and retrieval are described and the resulting data are given in tables 4 to 11.

Thermochemical Data for Gaseous Monoxides

The actinyl ions exhibit an unusually robust covalent bond which has a profound influence on their chemistry. Their electronic structure has been unravelled by the use of a variety of optical measurements and by photoelectron spectroscopy, which together establish the composition and role of the valence orbitals. The experimental energy level scheme can be compared with the results of molecular orbital calculations of varying degrees of sophistication, the most successful being SCF calculations incorporating the effects of relativity. An important contribution to the bonding comes from the pseudo-core 6p shell, which is important in determining the linearity of the ions. A new concept, the Inverse trans Influence, is introduced in this context. There is some evidence that (d-orbital π-bonding is more important than σ-bonding. The remarkable strength of the actinyl bond can be attributed to the presence in the valence shell of both f and d metal orbitals, giving each actinide-oxygen bond a formal bond order of three.

Electronic structure and bonding in actinyl ions

The first ionization potentials of the gaseous lanthanide metals and monoxides have been determined by electron impact from the appearance potentials of ionization efficiency curves. A method of simultaneous and intercomparative measurements with known standards was used and the results for the lanthanide metals are in excellent agreement with values obtained previously from spectroscopic and surface ionization studies. In the early part of the lanthanide sequence the ionization potentials of LnO(g) are less than those of Ln(g), whereas the converse is true in the latter part. The differences in the ionization potentials of LnO(g) and Ln(g) are simply related to the differences in the dissociation energies of LnO(g) and LnO+(g). Values of D0(LnO+) are derived. The nature of the chemical bonding in LnO(g) and LnO+(g) is examined for the lanthanide sequence by means of an electrostatic point‐charge model. The assumption of monotonic variation of the interatomic distance and the electrostatic repulsion param...

The thermodynamics of ionization of gaseous oxides; the first ionization potentials of the lanthanide metals and monoxides

A thermodynamic study of the tungsten-oxygen system at high temperatures1

The ionization potentials of the gaseous atoms, monoxides, and dioxides over the refractory oxides of Ti, Zr, Hf, Th, U, Y, and La have been obtained from ionization efficiency curves and appearance potentials by electron impact. A method of simultaneous and intercomparative measurements with known standards was used. The measured values for the gaseous metal atoms are in agreement with the spectroscopic values except for Zr and Hf which are about 0.4 eV lower. These results and some of previous studies show that the values for the monoxides are somewhat less than those for the metals, and the dioxides of those metals in their highest oxidation state are generally larger by 3–4 eV.

First ionization potentials of some refractory oxide vapors

Thermal expansion and phase transformations of the U3O8−z phase in air☆

A high-temperature study of the stoichiometry, phase behavior, vaporization characteristics, and thermodynamic properties of the cerium + oxygen system

R. J. Ackermann

Papers

The thermodynamics of ionization of gaseous oxides; the first ionization potentials of the lanthanide metals and monoxides

A thermodynamic study of the tungsten-oxygen system at high temperatures1

First ionization potentials of some refractory oxide vapors

Thermal expansion and phase transformations of the U3O8−z phase in air☆

A high-temperature study of the stoichiometry, phase behavior, vaporization characteristics, and thermodynamic properties of the cerium + oxygen system