The effect of substitution of 'Hg' at the Bi-site in Bi1.7V 8O16 on the phase formation and electrical properties has been studied. In Bi1.7-xHgxV8O16, single phase formation is achieved only for x ≤ 0.4 and all the phases crystallize in tetragonal structure. The dc electrical resistivity studies indicate that all the mercury substituted single phase compounds Bi 1.7-xHgxV8O16 are electrically semiconducting and the room temperature resistivity values increase with increasing mercury content. Alkali metals like lithium and sodium have been inserted successfully into the tunnels of Bi1.7V8O 16. The lithium intercalated phase Li2.7Bi 1.7V8O16 shows antiferromagnetic ordering, whereas the sodium intercalated phase NaBi1.7V8O 16 exhibits Pauli paramagnetic like behavior down to 4.5 K.

Upadhyayula V Varadaraju

Department Of Chemistry

Karthikeyan N. Marimuthu

ANTIFERROELECTRIC MATERIALS

Bismuth compounds

Electric properties

Magnetic properties

Mercury (metal)

Phase composition

Synthesis (chemical)

Antiferromagnetic ordering

Intercalation

Phase formation

Inorganic compounds

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IIT Madras

Materials Chemistry and Physics

A new niobium-substituted hollandite K2Ti5NbFe 2O16 has been synthesised for the first time. The compound is crystallised in tetragonal structure. A two to three orders change in electrical resistivity is observed with temperature as compared to the parent phase K2Ti6Fe2O16. The niobium-substituted phase shows antiferromagnetic ordering with TN = 37K at a field of 0.1T and the antiferromagnetic ordering disappears at higher field (0.2T) indicating field induced magnetic behaviour. The Mössbauer spectrum of K2Ti5NbFe2O16 shows majority of the Fe ions are 3+ oxidation state (96%). For the first time, we have intercalated lithium into K2Ti6M2O 16 (M = Cr, Fe and Ga) and K2Ti5NbFe 2O16 hollandite type phases using n-butyllithium in hexane. The estimated lithium content for all the phases are in the range 1.7-2.7mol per formula unit. © 2003 Elsevier B.V. All rights reserved.

Solid state studies on K2Ti6-xNbxFe 2O16 (x = 0 and 1) and lithium insertion into K 2Ti6M2O16 (M = Cr, Fe and Ga) and K2Ti5NbFe2O16 hollandite type phases

Alkali metals like Li and Na are inserted into the tunnels of anion excess fluorite related structure compound Bi2Te2W3O16 using n-butyllithium and NaN3, respectively without any perceptible change of crystal structure. The insertion process is not completely reversible. The alkali metal inserted phases have room temperature resistivity values three orders less than that of the parent phase. The parent phase Bi2Te2W3O16 shows anomalous increase in dielectric constant with temperature.

Alkali metal insertion and dielectric studies on anion excess fluorite related mixed oxide Bi2Te2W3O16

Hollandite oxides of the type Bi1.7-xPbxV8O16 have been synthesized. The electrical resistivity studies show that the conductivity improves upon Pb substitution. The feasibility of Li intercalation in the system has been established. Magnetic susceptibility studies on the pure and Li intercalated phases show that except for pure Bi1.7V8O16, all phases exhibit Pauli paramagnetism. No superconductivity is encountered down to 12 K in any of the phases. © 1998 Elsevier Science B.V. All rights reserved.

Materials Letters

Electrical and magnetic properties of pure and Li intercalated Bi1.7-xPbxV8O16 phases

Chemistry Letters

Superconductivity of Alkali Metal Intercalated Niobate with a Layered Perovskite Structure

Physica C: Superconductivity

A new metastable superconductor Li2Na1NyC60 prepared from azides

Solid state studies on Bi1.7-xHgxV8O 16 (x≤0.4) and magnetic properties of alkali metal inserted A xBi1.7V8O16 (A=Li and Na) hollandite type phases

Journal	Materials Chemistry and Physics
ISSN	02540584
Open Access	No