Temperature dependence of the ferroelectric properties of Y1-xbixmno3

A detailed study, by x-ray and piezoelectric techniques, of the ferroelectric transition in the compound Y1-xBixMnO3 is presented.Two transition temperatures are found in homogeneously bismuth-doped single crystals: 1) - the lower one T1 is associated with a diffuse ferroelectric transition and is strongly dependent on bismuth concentration x. 2) - the upper one T2 is independent of x: and not associated with ferroelectricity.Heterogeneous crystals, in which a separation between a bismuth-poor bulk and bismuth-rich surface layers occurs, behave like a two-phase structure. They possess two characteristic temperatures T1 and only temperature T2