Solid state studies on rare earth mixed oxide pyrochlores Er<inf>2</inf>(V<inf>1-x</inf> Fe<inf> x</inf> )<inf>4/3</inf> W<inf>2/3</inf>O<inf>7</inf>

Complete series of solid solutions exist in the mixed oxide pyrochlore system, Er 2 3+ (V 1-x 3+ Fe x 3+ )4/3 W 2 3/6+ O7, with the crystal structure changing from cubic to rhombohedral at x=0·25. The compounds are semiconductors at 300 K exhibiting p- or n-type behaviour depending on the value of x. The observed resistivity and Seebeck coefficient data as a function of temperature have been interpreted in terms of a hopping mechanism. © 1980 Indian Academy of Sciences.