Search

Layered pnictide oxides are an unusual class of compounds which have received little attention. The characteristic feature of these materials is the presence of pnictogen and oxygen atoms which are not bonded to each other and are considered to be anions. This class of compounds is made up of ternary pnictide oxides of alkaline or rare earth metals, and quaternary pnictide oxides of alkali or alkaline earth metal along with transition metals. This Comment discusses structure and bonding in this small group of compounds. Additionally, magnetic and electronic properties of many of the transition metal pnictide oxide compounds are presented.

There are a wide variety of ternary compounds, AxMyXz, where A = alkali or alkaline earth metal, M = semimetal or main group element and X = pnictide, that have been synthesized. For example the compounds Ba3AlSb3, Ca3AlSb3, Ca3AlSb3 and Ca5Al2Sb6 have been synthesized and their structures can be understood via the Zintl formalism which can be simply stated as the octet rule for all atoms. The structures can be generally formulated as A− + [(MX)−] so that the anionic units in these examples may be written as: (Al2Sb6)12-; (AlSb3)6- chains; a (Al2Sb6)10- network; and [(AlSb9- 4) + 4Sb3- + Sb7- 3). The Zintl concept has also been applied to ternary transition metal compounds such as the lanthanum transition metal pnictides and ternary transition metal chalcogenides. These structures and their related properties can be understood in terms of cations and complex polyatomic anionic units. The Zintl concept, as it applies to ternary pnictide compounds, will be presented and its extension to ternary tra...

Sodium intercalation compounds of YbOCI have been synthesized by reaction of Na-NH3 solutions with YbOCI (SmSI structure type). These materials have been characterized by powder X-ray diffraction and optical spectroscopy. An increase in the basal plane separation of ∼3 A indicates that cointercalation of NH3 occurs. Optical spectroscopy data show the appearance of two new absorption bands upon intercalation and is consistent with the reduction of Yb3+ to Yb2+. Synthesis, structure and optical properties of these new materials is discussed.

Magnetic susceptibility and electrical resistivity measurements have been made on the Zintl compound, Cal4MnBi11, for temperatures between 6 K and 300 K. The magnetic data are consistent with high spin Mn+3 for T < 100 K and a ferromagnetic transition is observed at ∼56 K. Although the Mn+3 ion has four unpaired spins in the paramagnetic regime, the ferromagnetic moment is considerably reduced. Resistivity data also display a transition at approximately 56 K.

Intercalation of tetrathiafulvalene (TTF), tetrathiatetracene (TTT), and related planar organo-sulfur electron donors into FeOCl results in a new series of low-dimensional materials with increased ...

For FeOCl and its intercalates, FeOCl.TTF1/9 (TTF=tetrathiafulvalene), FeOCl.TTN1/9 (TTN=tetrathianaphthalene), and FeOC1.TTT1/7 (TTT= tetrathiatetracene), the combination of X-ray powder diffraction data and Fe K-edge EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy provides a consistent picture of the structural changes of the FeOCl host upon intercalation. A structural model based upon the data obtained from both techniques is discussed, in which the intercalated radical cations are tilted at an angle 6 from the b axis (θ=25±5° for TTF, 42±5° for TTN, TTT). In the TTN and TTT intercalates, the radical cations are also tilted at an additional angle o from the ac plane (o = 14±5°).