A propos de la ferroeléctricité dans BaAl2O4

摘要: Abstract Structural, ferroelectric, pyroelectric, and optical properties of ceramics crystals BaAl2O4 have been investigated. A refinement the atomic positions has carried out from X-ray powder data. shows anomalous behavior dielectric pyroelectric properties: constant e′r is very weak; its maximal value at Curie temperature for a crystal oriented along hexagonal c-axis about 15 that ceramic compactness 0.89 around 7.5. The Curie-Weiss relatively weak (C = 125). spontaneous polarization Ps unexpected with respect to classical ferroelectric materials: increases decreasing Tc decreases again after having reached maximum 200 K. model based on ferrielectric supported by Landau equation proposed. La structure et les proprietes ferroelectriques, pyroelectriques optiques de ceramiques cristaux du compose ont ete etudiees. Un affinement des atomiques entrepris partir spectre diffraction X sur poudre. presente un comportement anormal dielectriques pyroelectriques: la constante dielectrique est faible, sa valeur maximale voisine pour 7,5 compacite 0,89. aussi relativement faible Le polarisation spontanee differe celui materiaux ferroelectriques "classiques": augmente lorsque T decroit en-dessous atteindre K suivi d'une decroissance. modele ferrielectrique s'appuyant relation pourrait justifier observees.