Influence of Co/W co-doping on structural and electrical properties of Na0.5Bi2.5Nb2O9 piezoelectric ceramics

Co/W co-doped Na_0.5Bi_2.5Nb_2-x(Co_1/3W_2/3)_xO₉ (NBNCW-x) ceramic samples were prepared by the conventional solid state reaction method. The electrical properties and crystal structure of the NBNCW-x ceramic samples were analyzed in detail. The XRD and Rietveld refinement results showed that the samples lattice distortion decreased with the increment of Co/W doping. The XPS results showed that the number of oxygen vacancies in the Na_0.5Bi_2.5Nb₂O₉ ceramics could be reduced by the substitution of a small amount of Co/W. The weakened lattice distortion and reduced number of oxygen vacancies of the Na_0.5Bi_2.5Nb₂O₉ ceramics synergistically contributed to its improved electrical properties. In particular, the Na_0.5Bi_2.5Nb_1.97(Co_1/3W_2/3)_0.03O₉ ceramic exhibited the best performance, and its T_c, d₃₃ and P_r were 780 °C, 24.9 pC/N and 12.6 μC/cm², respectively. The dielectric loss was only 3.3% at 550 °C. In addition, this ceramic exhibited excellent thermal stability, with the d₃₃ value of the ceramic being 95.2% of its original value when annealed at 750 °C. These properties indicate that the Co/W co-doped Na_0.5Bi_2.5Nb₂O₉-based ceramics have potential application in the high-temperature field.