TeO2

TeO2, known as tellurium dioxide or tellurium(IV) oxide, is an inorganic compound consisting of tellurium in the +4 oxidation state bonded to two oxide ions. It is typically a white to pale yellow crystalline solid that is insoluble in water. TeO2 exists in several crystalline forms depending on temperature and preparation, reflecting its tendency to adopt different polymorphs under different conditions. The material is relatively hard and brittle, with a high refractive index and notable optical anisotropy.

Preparation and properties

TeO2 is commonly prepared by oxidizing tellurium metal in air at elevated temperature or by the oxidation of tellurium compounds such as tellurium halides. It can also be formed by hydrolysis of certain tellurium halides. In solution, TeO2 demonstrates amphoteric behavior: it dissolves in hot alkali to give tellurite ions (TeO3^2−) and dissolves in acids to form tellurous acid (H2TeO3), illustrating its dual acid-base character.

Applications

TeO2 is used as a precursor in the synthesis of organotellurium compounds. It is also valued in optics for its high refractive index and birefringence, and crystalline TeO2 is employed in acousto-optic devices and other electro-optic applications, where its electro-optic and piezoelectric properties are exploited.

Occurrence and safety

Natural tellurium dioxide can occur as the mineral tellurite in telluride-rich ore deposits. TeO2 and its dust are toxic; exposure should be minimized, with appropriate precautions such as ventilation and protective equipment.

These characteristics make TeO2 an important oxide in both inorganic synthesis and optical technology, while requiring careful handling due to toxicity.