Ferroelectric oxy-fluoride(s) - of a wide range of materials of chiolite structure

摘要

Ferroelectric oxyfluorides of formulae (A(1-x)A'x)5.(M(1-y)M'y)3.Oz.F(14-z) (I) are new. A is Na; A' is Li, K, Ca, Sr, Y, Ag, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb or Bi; M is W; M' is Li, Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, In, Sn, Sb, Tc or Ta; x, y and z are integers or fractions such x is 0-0.20; y is 0-0.67, z is 7-10 and O/F is 1-2.5. Specific compsns. are Na5W309F5; Na5W2MoO9F5, Na5WNb2O7F7, Na5W2TiO7F7 and Na4.5Nd0.5W2NbO9F5. The compsns. are pref. in the form of ceramics, or crystals, esp. monocrystals. The monocrystalline form can be prepd. as transparent plates with mutually perpendicular ferroelectric-ferroelastic domains. The material can be used in systems dependent on the electro-optic, piezoelectric, pyroelectric and/or ferro elastic effects. These systems can be optical data stores, telecommunication fitters or radar delay lines, heat cameras and/or optical gates and memories. The materials are transparent and chemically stable and have ferroelectric properties at about 20 deg.C, some of which are novel.