Wyllieite-type Ag1.09Mn3.46(AsO4)3

Single crystals of wyllieite-type silver(I) manganese(II) tris­orthoarsenate(V), Ag1.09Mn3.46(AsO4)3, were grown by a solid-state reaction. The three-dimensional framework is made up from four Mn2+/Mn3+ cations surrounded octa­hedrally by O atoms. The MnO6 octa­hedra are linked through edge- and corner-sharing. Three independent AsO4 tetra­hedra are linked to the framework through common corners, delimiting channels along [100] in which two partly occupied Ag+ sites reside, one on an inversion centre and with an occupancy of 0.631 (4), the other on a general site and with an occupancy of 0.774 (3), both within distorted tetra­hedral environments. One of the Mn sites is also located on an inversion centre and is partly occupied, with an occupancy of 0.916 (5). Related compounds with alluaudite-type or rosemaryite-type structures are compared and discussed

Ionic behavior, Na+ mobility and infrared spectroscopy in Na7Cr4(P2O7)4PO4 material

The title compound, heptasodium tetrachromium(III) tetrakis(diphosphate) orthophosphate, was synthesized by solid state reaction. Its structure is isotypic with that of Na7M4(P2O7)4PO4 (M = In, Al) compounds and is made up from a three-dimensional [(CrP2O7)4PO4]7- framework with channels running along [001]. The Na+ cations are located in the voids of the framework. This compound has been investigated by X-ray diffraction and infrared (IR) spectroscopy. The conductivity measurements of the compound were carried out from 515 to 795 Kelvin using the frequency response analyzer with 0.05V amplitude signal over the range of 13MHz-5Hz. The conductivity of the sample at 574K is 0.45 10-6 S.cm-1. The activation energy Ea=0.73eV shows that Na7Cr4(P2O7)4PO4 is a medium ionic conductors. The monovalent cations conduction pathways in the crystal bulks are simulated by means of the bond valence model (BVS)

2-Amino-5-chloro­pyridinium cis-diaqua­dioxalatochromate(III) sesquihydrate

In the crystal structure of the title compound, (C5H6ClN2)[Cr(C2O4)2(H2O)2]·1.5H2O, the CrIII atom adopts a distorted octa­hedral geometry being coordinated by two O atoms of two cis water mol­ecules and four O atoms from two chelating oxalate dianions. The cis-diaqua­dioxalatochromate(III) anions, 2-amino-5-chloro­pyridinium cations and uncoordinated water mol­ecules are linked into a three-dimensional supra­molecular array by O—H⋯O and N—H⋯O hydrogen-bonding inter­actions. One of the two independent lattice water molecules is situated on a twofold rotation axis

Cobalt Phosphates and Applications

Cobalt phosphates with open framework present various physical performances in relation to their structures. In fact, the development of new materials that could potentially be ionic conductors or ion exchangers led us to examine the Co-P-O and A-Co-P-O crystallographic systems (A: monovalent cation) and their different methods of synthesis. This work consists first of all in highlighting the crystalline phases of cobalt phosphates. Indeed, many works related to the discovery of some of these materials with interesting properties, in particular ionic conductivity, motivated our research and encouraged us to collect several cobalt phosphates and to correlate structure-physical properties in particular electrical properties

Electrical and Vibrational Studies of Na 2

The complex impedance of Na2K2Cu(MoO4)3 material has been investigated in the temperature range of 653–753 K and in the frequency range of 40 Hz–5 MHz. Electrical behavior of the studied material is explained through an equivalent circuit model which takes into account the contributions of grains and grains boundaries. The number of vibrational modes was calculated using group theoretical approach. The infrared and Raman spectra have also been measured and vibrational assignment has been proposed

K0.12Na0.54Ag0.34Nb4O9AsO4

Potassium sodium silver tetra­niobium nona­oxide arsenate, K0.12Na0.54Ag0.34Nb4AsO13, synthesized by solid-state reaction at 1123 K, adopts a three-dimensional framework delimiting tunnels running along [001] in which occupationally disordered sodium, silver, and potassium ions are located. Of the 11 atoms in the asymmetric unit (two Nb, one As, one Ag, one K, one Na and fiveO), nine are located on special positions: one Nb and the K, Ag, Na and two O atoms are situated on mirror planes, the other Nb is on a twofold rotation axis, and the As atom and one O atom are on sites of m2m symmetry

Disodium tris­(dioxidomolybdenum) bis­(diarsenate)

The asymmetric unit of the title compound, Na2(MoO2)3(As2O7)2, is composed of two cyclic MoAs2O11 units and an MoO6 corner-sharing octa­hedron. The anionic framework can be decomposed into two types of layers, viz. MoO2As2O7 and Mo2As2O14, which use mixed Mo—O—As and As—O—Mo bridges to achieve a new three-dimensional structure with two types of large channels in which the Na+ cations are located. Two O atoms are disordered and are located in two positions close to their initial positions with occupancy ratios of 0.612 (17):0.388 (17) and 0.703 (12):0.298 (12)

La variété β-NaMoO2(AsO4)

The title compound, sodium dioxidomolybdenum(VI) arsenate(V), β-NaMoO2AsO4, was prepared by solid-state reaction at 953 K. In the crystal structure, the AsO4 tetra­hedra and MoO6 octa­hedra (both with m symmetry) share corner atoms to form a three-dimensional framework that delimits cavities parallel to [010] where disordered six-coordinated sodium cations (half-occupation) are located. Structural relationships between the different orthoarsenates of the AMoO2AsO4 series (A = Ag, Li, Na, K and Rb) are discussed

K0.8Ag0.2Nb4O9AsO4

The title compound, potassium silver tetra­niobium nona­oxide arsenate, K0.8Ag0.2Nb4O9AsO4, was prepared by a solid-state reaction at 1183 K. The structure consists of infinite (Nb2AsO14)n chains parallel to the b axis and cross-linked by corner sharing via pairs of edge-sharing octa­hedra. Each pair links together four infinite chains to form a three-dimensional framework. The K+ and Ag+ ions partially occupy several independent close positions in the inter­connected cavities delimited by the framework. K0.8Ag0.2Nb4O9AsO4 is likely to exhibit fast alkali-ion mobility and ion-exchange properties. The Wyckoff symbols of special positions are as follows: one Nb 8e, one Nb 8g, As 4c, two K 8f, one Ag 8f, one Ag 4c, one O 8g, one O 4c

Correlation between Structure, Electrical, and Magnetic Properties of Some Alkali-Oxide Materials

In this chapter, the correlation between structure and electrical properties of Na2MP1.5As0.5O7 (MII = Co and Cu) are treated. The structural study shows that the cobalt and copper isotype materials can be crystallized in the tetragonal and monoclinic systems, respectively. The electrical study using impedance spectroscopy technique showed that these mixed diphosphate diarsenates are fast electrical conductors; however, the cobalt material exhibited more conductive property than the copper compound. In addition, the powder perovskite manganites La0.7M0.2M’0.1MnO3 (M = Sr, Ba and M’ = Na, Ag and K) have been prepared using the conventional solid-state reaction. The structural, magnetic, and magnetocaloric properties of these perovskite manganites compounds were studied extensively by means of X-ray powder diffraction (XRD) and magnetic measurements. These samples were crystallized in the distorted rhombohedral system with R3c space group. The variation of magnetization (M) vs. temperature (T) reveals that all compounds exhibit a second-order ferromagnetic to paramagnetic phase transition in the vicinity of the Curie temperature (TC). A maximum magnetic entropy change, ΔSMMax, of 4.07 J kg−1 K−1 around 345 K was obtained in La0.7Sr0.2Na0.1MnO3 sample upon a magnetic field change of 5 T. The ΔSMMax values of La0.7Ba0.2M’0.1MnO3 are smaller in magnitude compared to La0.7Sr0.2M’0.1MnO3 samples and occur at lower temperatures