Substituted barium titanate and barium strontium titanate ferroelectric compositions

This invention provides the three novel La,Fe, La,Cr and Sm,Fe substituted barium titanate solid solution ferroelectric compositions with the formula Ba_1-xLn_xTi_1-xM_xO₃ wherein when Ln is La, M is Fe or Cr, when Ln is Sm, M is Fe and x is from about 0.02 to about 0.06 and mixtures thereof, the novel La,Fe substituted barium strontium titanate solid solution ferroelectric compositions with the formula (Ba_1-ySr_y)_1-xLa_xTi_1-xFe_x O₃ wherein y is greater than zero and less than about 0.6 and x is from about 0.01 to about 0.06 and the novel La,Al substituted barium strontium titanate solid solution ferroelectric compositions with the formula (Ba_1-ySr_y)_1-xLa_x Ti_{1-x/4 3a/4}Al_a(x-a)/4O₃ wherein denotes a vacancy, y is greater than zero and less than about 0.6, a is from about 0.01 to about 0.06 and x is from 0.02 to about 0.10 with the proviso that x is greater than or equal to a. These low loss tunable ferroelectric compositions are especially useful in tunable microwave thin film devices which fall into three types: interdigital and trilayer capacitors, coplanar waveguides and microstrips.