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Converters & Calculators
Why Is Hafnium Smaller Than Zirconium
The geochemical properties of Hf and Zr are similar. The ionic radius of Hf is almost the same as that of Zr. All Zr minerals contain Hf, and pure Hf minerals have not been documented.
Hf concentrations in minerals rarely exceed those of Zr, except for specific types of Thortveitite. Zircon (SiO4) and Baddeleyite (ZrO2) are the principal sources of Hf. They typically contain up to 2%. Certain Norwegian zircon minerals have recorded Hf levels of 20%. Hafnium is predominantly lithophilic. It occurs in oxides and silicates as the Hf ion.
Hafnium can serve as an indicator for Zr mineralisation. Elevated Hf values indicate the presence of felsic rocks, particularly intrusive masses. The resistant nature of Hf minerals limits the dissolution of Hf in natural water. Complexes with sulphates, fluorides and chlorides show low solubility in aqueous solution, and natural organic substances can form complexes that increase Hf concentration in freshwater. Hafnium usually exists in natural waters at concentrations below 0.1 µg l-1. Wastewater represents the primary anthropogenic source of Hf. Hf is utilised in the manufacture of incandescent lamp filaments, X‑ray cathode tubes, reactor control rods, and in alloying with Ti, Nb, Ta and Fe, as well as in the ceramics industry. Several studies from the 1960s and 1970s indicated that Hf concentrations in industrial regions do not exceed natural levels. Consequently, geological sources of Hf are more significant than anthropogenic ones.
Hafnium has no known biological function. Limited data exist on the toxicity of Hf. It is generally considered to have low toxicity, and no adverse environmental impacts have been reported. Given that insufficient data exist concerning the effects of Hf on human health, it should be regarded as potentially toxic.
Hafnium oxide (Hafnia) has been extensively studied as a high‑k dielectric. It is used as a replacement for the standard gate dielectric SiO2 in the manufacture of high‑density logic and memory devices.
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