Some Tungsten–Bronze Compounds in the BaO–Nd2O3–TiO2–Ta2O5 System

Some dielectric oxides have been synthesized and characterized in the BaO–Nd2O3–TiO2–Ta2O5 system. Through X-ray powder diffraction analysis, Ba4Nd2Ti4Ta6O30 and Ba5NdTi3Ta7O30 are identified as tetragonal tungsten–bronze compounds, and their lattice constants are a=b=12.4007(7) ?, c=3.9030(3) ? and a=b=12.4826(6) ?, c=3.9295(5) ?, respectively. The possible space group is P4bm. The polycrystalline samples of these compounds exhibit high dielectric constant (137 ~ 160) and low dielectric loss, tan delta<7×10-4 at 1 MHz.