الفهرس 
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Abstract
Phosphate compounds find wide applications in many technological fields such as in nonlinear optics, electronics industry, biocompatible materials, superionic conductors, ion exchangers, and in low thermal expansion materials. A great deal of attention has been devoted to new synthesis strategies for the phosphate compounds.
The chemistry of transition metal phosphates has been, till now, a subject of increasing interest because a variety of compounds with different structures and properties can be prepared. By limiting our attention to phosphates of tetravalent transition metals and, among them, only the layered structures, the number of already known compounds is very high. The general formula of these compounds can be written as M(HPO4)2.nH2O(where M=tetravalent metal such as Zr, Ti, Hf). A special attention will be paid to titanium phosphate, which is the subject of the present work.
Titanium phosphates can be prepared by different methods including the traditional and the sol-gel process. Different forms of titanium phosphates in amorphous or crystalline states were produced depending on the method of preparation, the precursor’s materials, and the condition of reaction such as the medium of reactions, temperature, pH value, time of treatment, and etc. Ti (IV) phosphate is generally obtained as an amorphous product precipitated from solution of phosphate and a titanium (IV) compound. Crystalline materials have been obtained by two different procedures. In 1967, Alberti et al showed that if the amorphous material is refluxed in phosphoric acid, a crystalline product is formed. However, to get a well crystallized product, refluxing times of over 350h. in 12M H3PO4 were needed. According to the other method, the crystalline product is obtained directly by slow decomposition of titanium-fluoro complex in the presence of phosphoric acid. Two different crystalline phases of layered titanium phosphate have been characterized α-Ti (HPO4)2.H2O (α-TiP), γ-Ti (HPO4)2.2H2O (γ-TiP).