Sol–gel derived Bi2NiNb2O9 pyrochlore: Synthesis, characterization and dielectric properties

The Pechini method was used for the first time to synthesize the phase-pure nickel-containing cubic pyrochlore Bi₂NiNb₂O₉ (space group Fd-3m, a = 10.5371(5) Å), while the solid-phase reaction method provided no possibility to obtain impurities-free pyrochlore. At a synthesis temperature of 950°С, low-porosity ceramics with indistinct grain boundaries were formed. The results of elemental mapping indicated a uniform distribution of metal atoms on the surface of the sample. The X-ray energy dispersive analysis showed that the chemical composition of the synthesized sample corresponded to the predetermined theoretical composition. The calcination of the sample synthesized by the Pechini method was studied by the thermal analysis up to 1100°С. The functional composition of intermediate synthesis products was analyzed by vibrational spectroscopy (FTIR). In the FTIR spectrum of pyrochlore (4000–400 cm⁻¹), absorption bands were identified at 829, 540, 654, and 490 cm⁻¹. The dielectric properties of the pyrochlore were studied using an impedance spectroscopy. Pyrochlore Bi₂NiNb₂O₉ has the high relative dielectric permittivity of 145 and low dielectric losses of 0.001 (at 24°С, 1 MHz), which make it a promising for dielectric in multilayer ceramic capacitors.