Magnetic and electrical properties of Cu substituted La1-xCaxCoO3 crystals

La1-xCaxCo1-yCuyO3-δ polycrystals have been prepared in the compositional range 0<y<0.1; 0<x<0.5 using the citrate method. For y=0, a transition to metallic (impurity band) conduction is observed at xc=0.45. All other compounds are semiconducting (∂ρ/∂T<0), show variable range hopping (ln ρ similar T-1/4) and a spin-glass-like behaviour except for T=4.2 K. A field-induced antiferromagnetic low spin/spin-glass-like mixed spin transition is observed, yielding 0.12 meV as an estimate for the ls/hs energy gap. (orig.)