Noval tunable ferroelectric compositions:: Ba1-xLnxTi1-xMxO3 (Ln = La, Sm, Gd, Dy, M = Al, Fe, Cr)

Ba1-xLaxTi1-xFexO3-type solid solutions are prepared. BaTiO3 remains as tetragonal phase up to about 5 mol% LaFeO3. For x greater than or equal to 0.06, the structure changes to cubic at room temperature. The phase change shifts the Curie temperature to lower value and increase the tunability at room temperature (tunability is defined as Delta epsilon/epsilon(0) where Delta epsilon is the change in the dielectric constant under applied voltage, and epsilon(0) is dielectric constant with no applied voltage). Doping of other accepters (Al, Cr) and donor (Sm, Gd, Dy) ions has the same effect although with varying levels of tuning. BaTiO3:4% LaFe has the highest tunability among the studied systems, which is even higher than that of Ba0.6Sr0.4TiO3. (C) 2000 Editions scientifiques et medicales Elsevier SAS. All rights reserved.