Tungsten bronze structure dielectric material is the important dielectric system only following perovskite, with complex crystal structure and rich ferroelectric phase transition and dielectric relaxation characteristics, which is potential multiferroic material and it has unique properties of excellent ferroelectric, piezoelectric, pyroelectric and nonlinear optics, etc., has gained more and more attention. In recent years, some researchers try to introduce Fe, Co, Ni and other magnetic ions to tungsten bronze niobate ferroelectrics, and found some multiferroic materials have both ferroelectricity and ferromagnetism at room temperature.

 

However, these ceramic materials require high temperature sintering, the sintering process on the one hand easily leads to changes in iron valence and the generation of oxygen vacancies; on the other hand, high-temperature sintering ion distribution is relatively disordered, and the subsequent cooling rate is usually faster, making the high temperature disordered state maintain a low temperature. As we all know, the annealing process is an important means to control the metal material structure and properties. Similarly annealing also has many applications in the ceramic material, such as Xia reported that the impact of annealing on lead-based relaxor ferroelectric properties, it’s found that peak dielectric constant and piezoelectric properties improved after annealing lead-based relaxor ferroelectrics significantly. There are more and more studies of ceramics annealing process in recent years.

 

Because of the complex structure of the tungsten bronze, tungsten bronzes ceramics typically contain a variety of ions in the A, B bit, and it may contain different valence ions (such as iron or titanium), the sintering temperature is likely to cause changes in ion valence and generate oxygen vacancies and affects the distribution of ions. The content of oxygen vacancies and the degree of ions ordered the distribution have great impacts on its corresponding ion tungsten bronze structure, dielectric properties, ferroelectric properties. Tungsten bronze structure is relatively complex, the annealing treatment will help to improve that the tungsten bronze niobate large ions occupy large clearance position and small ions occupy a small gap position. At the same time, under different atmosphere, annealing can also effectively control the concentration of oxygen vacancies niobate. At present, there are a lot of tungsten bronze ceramic studies, but there is little about annealing effect on the tungsten bronze ceramics structure and properties. Thus, firstly prepared iron-tungsten bronze niobate Ba₄Nd₂Fe₂Nb₈O₃₀ by solid-phase method, then annealed ceramic in oxygen and nitrogen after being sintered, study about annealing treatment effects on its structure, dielectric properties, ferroelectric properties.