Influence de divers types de substitutions cationiques sur les propriétés diélectriques de niobates de structure “bronzes oxygénés de tungstène quadratiques”

The value of the ferroelectric Curie temperature in compounds with the “tetragonal tungsten bronze structure” is related to the steric effect of large alkali or alkaline-earth cations in the lattice tunnels, to the covalency of the transition element-oxygen bonds, and to the introduction of Li⁺ ions, which due to their small size are able to occupy the nine coordination sites of the structure anisotropically.