钨青铜结构Ba6Zn0.67M9.33O30(M=Nb,Ta)的合成与介电特性

Two compounds Ba₆Zn_0.67M_9.33O₃ and Ba₆Zn_0.67M_9.33O₃₀ with tungsten bronze structure were synthesized in the BaO-ZnO-Nb₂O₅/Ta₂O₅ systems by the conventional high temperature solid-state reaction.The structure and dielectric properties of Ba₆Zn_0.67M_9.33O₃ and Ba₆Zn_0.67M_9.33O₃₀ were determined by X-ray powder diffraction,scanning electron microscope and dielectric measurements.The results show that Ba₆Zn_0.67M_9.33O₃₀ belongs to paraelectric phase of fully filled tetragonal tungsten bronze structure at room temperature with unit cell parameters a:1.26256(4) nm, c:0.39698(2) nm. The room temperature dielectric constant (ε) of Ba₆Zn_0.67M_9.33O₃₀ ceramic reached 108 combined with a low dielectric loss of 0.005 at 1 MHz. While Ba₆Zn_0.67M_9.33O₃ belongs to fully filled tetragonal tungsten bronze structure at room temperature with the unit cell parameters a:1.25940 (3) nm, c=0.40008(2) nm. Ba₆Zn_0.67M_9.33O₃₀ ceramic shows significant relaxor behaviors, and the phase transition from ferroelectric to paraelectric occurred at 55℃ (at 1 MHz). The room temperature dielectric constant (ε) of ceramic reached 570 at 1 MHz.

Synthesis and Dielectric Properties of Tungsten Bronze Structure Compounds Ba6Zn0.67M9.33O30(M=Nb,Ta)