Гадолиний-оксид титана (Gd2Ti2O7)

Identification

Gadolinium titanium oxide (Gd2Ti2O7) is a complex oxide with a pyrochlore structure, CAS number 12024-89-4, EC number 234-699-0. Chemical formula Gd,O,Ti (Gd2Ti2O7).

Synonyms

• Gadolinium titanium oxide (Gd2Ti2O7)
• Gadolinium titanate(IV) (Gd2(Ti2O7))
• Gadolinium titanate (Gd2Ti2O7)

Basic Attributes

• Molecular weight: 602.1
• Exact weight: 603.646
• PSA Specs: 189.57
• XLogP3: -1.0692

Substance class and structure

The compound belongs to the family of rare earth titanate pyrochlores with the general formula A2B2O7, where position A is occupied by gadolinium and position B by titanium. The pyrochlore structure is formed by alternating coordination polyhedra of cations A and B, which determines its resistance to structural distortions.

Scope of application

Gd2Ti2O7 is considered as a promising matrix for the immobilization (vitrification) of high-level nuclear waste, primarily actinides - plutonium and minor actinides. Pyrochlores based on gadolinium and titanium are also being studied as materials for fast ionic conductivity and as a functional matrix for luminescent sensitization of waste when monitoring the condition of storage facilities.

Radiation resistance

A key characteristic for nuclear applications is resistance to radiation-induced amorphization. Gd2Ti2O7 amorphizes already at a relatively low absorbed dose - about 0.2 displacement per atom at room temperature, the critical amorphization temperature is about 1100 K. The replacement of part of the titanium with zirconium in the Gd2(ZrxTi1-x)2O7 system systematically increases the resistance to radiation-induced amorphization, which makes it possible to select the composition of the matrix for a specific type of waste.

Technological aspects

The material is obtained by methods of solid-phase synthesis, hot isostatic pressing of glass ceramics and self-propagating high-temperature synthesis; the latter method is used, in particular, for the rapid immobilization of radioactive soil waste simulants.

Storage

Store in a dry place, in a closed container, as an inert refractory ceramic powder. There are no special requirements for temperature conditions - the material is chemically and thermally stable under normal storage conditions; Avoid prolonged contact with moisture to maintain the flowability of the powder.

Gadolinium as an element

The half-filled 4f shell gives the Gd3+ ion seven unpaired electrons and, as a result, one of the highest magnetic moments of all elements. In compounds, gadolinium exhibits a stable oxidation state of +3, and is extracted from the minerals monazite and bastnaesite using ion exchange and liquid extraction methods together with other lanthanides. Among stable elements, gadolinium has the largest thermal neutron capture cross section, which determines its role in nuclear technology. Gadolinium metal is ferromagnetic below the Curie point, which is close to room temperature (about 20 °C), above which it becomes paramagnetic.