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Metal–Insulator Transition in A x VS 2 Compounds
Author(s) -
Poddar P.,
Rastogi A.K.
Publication year - 2000
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(200003)218:1<229::aid-pssb229>3.0.co;2-o
Subject(s) - materials science , ternary operation , metal , condensed matter physics , conductivity , hexagonal crystal system , electrical resistivity and conductivity , metal–insulator transition , thermoelectric effect , insulator (electricity) , transition temperature , transition metal , thermodynamics , crystallography , chemistry , metallurgy , composite material , superconductivity , catalysis , biochemistry , physics , computer science , electrical engineering , programming language , engineering
The ternary transition metal compounds Al x VS 2 (0.25 ≤ x ≤ 0.50) have structures derived from hexagonal CdI 2 –NiAs with an enlarged 2 a 0 × 2 a 0 × 2 c 0 × (2T) 2 a 0 × 2 a 0 × 3 c 0 × (3T) basic cell alongwith structural distortions. Transport properties are very sensitive to the temperature of preparation. The low temperature annealed (LT) phases show higher conductivity at room temperature than high temperature quenched (HT) phases. On cooling, these metal‐like phases show two different transitions in conductivity, first one around 160 to 180 K giving insulator‐like phases and the second around 30 to 40 K where the resistance shows a sharp decrease on cooling. The phases quenched above 1000 °C give widely different transport and thermoelectric properties depending upon Al concentration with metallic ( x = 0.50), insulating ( x = 0.33) or semiconducting ( x = 0.25) behaviour. The magnetic susceptibility of all these phases shows strong temperature dependence above 80 K. These properties are discussed in terms of localization of carriers on V–V clusters and structural disorder.