Structural and Dielectric Properties of Ba_5R NiNb_9O_(30)(R=La, Nd and Sm) Ceramics

摘要

Three novel Ba_5R NiNb_9O_(30) ( R = La, Nd and Sm) ceramics were prepared and characterized in the BaO-R_2O_3-NiO-Nb_2O_5 system. All three compounds areparaelectjicphases adopting the. filled tetragonal tungsten bronze (TB) structure at room temperature . At 1 MHz, Ba_5R NiNb_9O_(30) ceramics have a high dielectric constants in the range 193-245.3, a low dielectric loss in range 0.0059-0.0087, and the temperature coefficients of the dielectric constant (tau_e) in the range - 1 140-1 310 X 10~(-6) centre dot deg C. Their temperature coefficients of the dielectric constant are significantly reduced compared to those of Ba_5R NiNb_9O_(30) (R= La, Nd, Sm) ceramics.