Pb5Ge3O11 Research Articles

Thirty years of research in ferroelectric oxyfluorides

Abstract About sixty ferroelectric oxyfluoride phases are presently known. They belong to two different families: - the “true” ferroelectric oxyfluorides with a relatively high F/O value (e.g. Rb3 MoO3 F3, Na5W3O9F5, Pb5W3O9F10, Bi2TiO4F2,…); - the compounds derived from ferroelectric oxides (perovskite, tetragonal tungsten bronze, pyrochlore, LiTaO3, Pb5 Ge3 O11, …) by continuous F-O substitution. The decrease in the Curie temperature with the fluorine rate is quite sharp for phases with corner linked octahedra, in which ferroelectricity is directly related to the length and covalency of the M-X (X=O, F) bonds. In the other cases the nature of the cations substituted to preserve electric neutrality has to be considered. Some of these materials have high performances, as dielectric for type I or II ceramic capacitors. All so far known ferroelectric oxyfluorides are indexed with their Curie temperature.

Liquid-Phase-Sintering of Barium Titanate and Its Modified Ceramics with Addition of Pb5Ge3O11

The liquid-phase-sintering effect has been examined in preparing BaTiO3 (BT) and its related ceramics. Lead germanate Pb5Ge3O11 (PG) was used as a bonding-phase material because of its low melting point. The dielectric constant 1230 and loss tangent 0.019 were obtained in BT-PG composite ceramics added with 10 wt% PG. The BT-BTS (Ba(Ti, Sn)O3)-PG composites, including in homogeneous two-phase, are obviously promising for improving the temperature characteristics of dielectric composite ceramics.