Many niobate crystals with tungsten bronze structure (TB) are excellent photorefractive materials, such as strontium barium niobate (Sr_xBa_1-xNb₂O₆, SBN), lead barium niobate (Pb_1-xBa_xNb₂O₆, PBN) , lithium potassium niobate (K₂Li_2-xNb_{5 + x}O_{15 + 2x}, KLN), barium sodium niobate (Ba₂NaNb₅O₁₅, BNN), strontium barium potassium sodium niobate ((K₂Na_1-x) ₂ (Sr_yBa_1-y) _n-2Nb₂O₆ KNSBN) newly-grown calcium and strontium barium niobate (Ca_xSr_yBa_1-x-yNb₂O₆, CSBN), etc. Since there are a lot of space in its internal structure, the quality of these crystal materials can be further improved by molecular design or doping or to change their each kind of properties (such as photorefractive characteristics of crystal, etc.). In addition to water-insoluble and stable physical and chemical properties, the majority of tungsten bronze niobate also has excellent electro-optical or nonlinear optical properties. Such as a relatively large electro-optic coefficient and relatively low half-wave voltage. In view of these excellent properties of niobate with tungsten bronze structure, it is being widely used in laser frequency, electro-optic modulator, associative memory storage, optical information processing, superconducting, humidity sensors, solid fuel cells and other fields.

 

General chemical formula of the tungsten bronze structure crystal is A_xB₁₀O₃₀, A can be cation with valent of one, two, three; B can be Nb, Ta, Ti, W and other positive ions, depending on the x, it may be classified as monoclinic, orthogonal, tetragonal crystals, hexagonal and cubic structure. The tungsten bronze structure generally called mainly refers to the tetragonal tungsten bronze structure. Structural formula of tungsten bronze niobate crystals can also be written as (A1) 2 (A2) 4 (C) 4Nb10O30: Nb - O octahedron constitutes lattice framework, and there are three different gaps of respectively with position 12 of A1, position15 of A2, position 9 of C. Gaps of A1, A2 and C can be filled with different valence of cation, to form a variety of compounds of tungsten bronze structure.