The tungsten bronze (TB) crystal material, due to good optical effects, electrical properties and blastic phase boundary and so on, has been widely used in the technical field of laser frequency doubling, optical modulator, optical information processing, superconducting, humidity sensors, fuel cells and other solids. Molecular design of TB crystal material is to design on the atomic level, explore and synthetic crystalline material of the target structure based on the understanding of its structure. In recent years, this area has made a lot of new results, which becomes an effective means of research and development and improved performance of this type of crystal material.

 

Tetragonal tungsten bronze (TTB) crystal is relative common of tungsten bronze type crystals, (many rhombic TB structure is a superstructure of TTB structure), which is widely used. So the commonly known TB crystal mainly refers to the TTB crystals. the structure projection of C-axis shown in FIG. B-O octahedra corner-top connection formed pentagonal, square and triangular pores. They are called A1, A2 and C positions. The thick solid line drawn is a unit cell, wherein: the number of void ratio down to A1: A2: C = 4: 2: 4, ie there are10 positions of A totally; and 10 positions of B and 30 of O^{2 -}.

 

B position can be divided into two B1 position (cell edges midpoint) and eight B2 position (cell interior) based on symmetric types. C axis translation period equals to the height of a B-O octahedron . In the structure: coordination number of A2 and O^2- may be 9,10,11,15, ligand effect of A2, C, B and O2- respectively are 12,9 and 6.

 

Therefore, the formula of TB structure is (A1) 1 (A 2) 2C4 (B1) 2 (B2) 8O30. When six A1, A2 positions are not filled with cation and C position is completely empty, it is called not filled structure; when six A1, A2 positions are all filled with cation and C position is completely empty, it is called full structure; When six A1, A2 positions and C position are all filled with cation, it is called completely filled structure.