Synthesis and properties of solid solutions of bismuth titanate with pyrochlore structure

The results of the synthesis of zinc-doped bismuth titanate with the pyrochloretype structure by combustion of nitrate-organic precursors method are presented. The homogeneity range of compounds Bi1.6Ti2ZnxO7-δ (0.1 ≤ х ≤ 0.5) was defined by X-ray and SEM (scanning electron microscopy) methods.The zinc atoms were distributed in the bismuth cation sites mainly. It was determined by the experimental pycnometric density of single-phaseBi1.6ZnxTi2O7-δ ( x = 0.4, 0.5) powder comparison with their densities calculated for the different versions of zinc atoms distribution in the cation sites of thepyrochlore structure ( Fd 3m ). The lattice parameter decreases from 10.331 Å to10.310 Å with zinc content Bi1.6ZnхTi2O7-δ increasing from х = 0.1 to х = 0.3- 0.5, this is consistent with proposed models of cation distribution.The range of Bi1.6ZnхTi2O7-δ stability ( t ≤ 1235 °С) was determined by differential scanning calorimetry (DSC) and thermal gravimetry (TG) methods. The phases of pyrochlore, layer perovskite (Bi4Ti3-хZnxО12-δ) and titanium dioxide were found at the melt crystallization.The total conductivity of Bi1.6Ti2ZnxO7-δ (0.1 ≤ х ≤ 0.5) with the pyrochlore-type structure was investigated. The temperature dependence of the conductivity obeys the Arrhenius law with the activation energy E a = 1.10 eV. The conductivities of the zinc-doped samples grow up with zinc content increased to x = 0.3 at 160-760 °C. We assume this may be associated with the increase of the mobile oxygen atoms (O`) number.