, Volume 25, Issue 1-2, pp 145-175

Superconducting and normal state properties of Li1+x Ti2−x O4 spinel compounds. I. Preparation, crystallography, superconducting properties, electrical resistivity, dielectric behavior, and magnetic susceptibility

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Abstract

LiTi 2 O 4 is one end member of the homogeneity range of the spinel phase Li 1+x Ti 2−x O 4 (0≤x≤1/3) and is superconducting at temperatures up to 13.7 K. Various measurements were carried out in order to characterize the superconducting and normal state properties of LiTi 2 O 4 and of other compositions within the homogeneity range of the spinel phase. These measurements establish LiTi 2 O 4 as ad-band superconductor and show thatT c decreases to <1.5 K forx≳0.1. This disappearance of superconductivity with increasingx was found to be correlated with anomalous changes in the lattice parameter with composition, and, from electrical resistivity measurements, is tentatively attributed to the occurrence of a composition-induced metal-semiconductor transition atx≈0.1. The metallic character of LiTi 2 O 4 and the composition dependence of the observed electrical properties are shown to follow from crystallographic considerations.

Research sponsored by the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under AFOSR Contract Number AFOSR/F-44620-C-0017.