Relation structure-metallicity in Bi-substituted multilayers ranging from BaPbO 3 to Ba 2PbO 4

Abstract

The relation structure-metallicity is explored in the phase diagram delimited by the compounds BaPbO 3, BaBiO 3, two perovskite structures, Ba 2PbO 4 which has a tetragonal La 2CuO 4-type structure, and Ba 2(Ba 2 3 Bi 1 3 )BiO 6−δ , the actual cubic double perovskite structure in which crystallizes the compound of chemical formula “Ba 2BiO 4”. Whereas a transition from metal to semiconductor is observed upon substituting Bi for Pb in the perovskite structure, all compounds along the axis going from Ba 2PbO 4 to Ba 2(Ba 2 3 Bi 1 3 )BiO 6−δ corners are found insulating. The metalinsulator transition on going from BaPbO 3 to Ba 2PbO 4 seems to be due to a slight expansion of the PbO 6 octahedra. New materials are characterized by X-ray, scanning electron microscope coupled with X-fluorescence, and infrared reflectivity spectroscopy to check the screening of phonons by the plasmon in conducting samples. Decreasing the Ba Pb ratio between 2 and 1 allows the formation of bidimensional conducting structures. No superconducting range has been found down to 4 K up to now upon substituting Pb for Bi and K for Ba in the multi-layers series on starting from Ba 4Pb 3O 10.