Hafnium oxide (IV)

Hafnium oxide
Hafnium oxide
Are common
Systematic ; name	hafnium oxide (IV)
Traditional names	hafnium oxide
Chem. formula	HfO 2
Physical properties
condition	white crystals
Molar mass	210.19 g / mol
Density	9.68 g / cm³
Thermal properties
T. melt.	2780; 2790 ° C
T. Kip.	5400 ° C
Mol heat capacity	60.2 J / (mol · K)
Education enthalpy	-1117 kJ / mol
Structure
Crystal structure	monoclinic, tetragonal, cubic
Classification
Reg. CAS number	12055-23-1
Pubchem
Reg. EINECS number
SMILES
Inchi
Chemspider
Security
NFPA 704	0 one 0

Hafnium (IV) oxide is a binary inorganic compound of a metal of hafnium and oxygen with the formula HfO ₂ , colorless crystals or a white powder, insoluble in water, from solutions of salts is released in the form of a hydrate.

Content

Getting

Burning metallic hafnium in oxygen :

{\mathsf {Hf+O_{2}\ {\xrightarrow {700^{o}C}}\ HfO_{2}}}.

{\ displaystyle {\ mathsf {Hf + O_ {2} \ {\ xrightarrow {700 ^ {o} C}} \ HfO_ {2}}}.}

Overheated vapor to hafnium metal:

{\mathsf {Hf+2H_{2}O\ {\xrightarrow {300^{o}C}}\ HfO_{2}+2H_{2}}}.

{\ displaystyle {\ mathsf {Hf + 2H_ {2} O \ {\ xrightarrow {300 ^ {o} C}} \ HfO_ {2} + 2H_ {2}}}.}

Decomposition when heated dihydroxide-hafnium oxide :

{\mathsf {HfO(OH)_{2}\ {\xrightarrow {600-1000^{o}C}}\ HfO_{2}+H_{2}O}}.

{\ displaystyle {\ mathsf {HfO (OH) _ {2} \ {\ xrightarrow {600-1000 ^ {o} C}} \ HfO_ {2} + H_ {2} O}}.}

Oxidation of hafnium (IV) chloride with oxygen:

{\mathsf {HfCl_{4}+O_{2}\ {\xrightarrow {500^{o}C}}\ HfO_{2}+2Cl_{2}}}.

{\ displaystyle {\ mathsf {HfCl_ {4} + O_ {2} \ {\ xrightarrow {500 ^ {o} C}} \ HfO_ {2} + 2Cl_ {2}}}.}

Decomposition while heating the oxide of hafnium :

{\mathsf {2HfOCl_{2}\ {\xrightarrow {300^{o}C}}\ HfO_{2}+HfCl_{4}}}.

{\ displaystyle {\ mathsf {2HfOCl_ {2} \ {\ xrightarrow {300 ^ {o} C}} \ HfO_ {2} + HfCl_ {4}}}.}

Decomposition of superheated hafnium dichloride oxide :

{\mathsf {HfOCl_{2}+H_{2}O\ {\xrightarrow {300^{o}C}}\ HfO_{2}+2HCl}}.

{\ displaystyle {\ mathsf {HfOCl_ {2} + H_ {2} O \ {\ xrightarrow {300 ^ {o} C}} \ HfO_ {2} + 2HCl}}.}

Pyrolysis of oxalate , sulfate and other salts of hafnium:

{\mathsf {Hf(C_{2}O_{4})_{2}\ {\xrightarrow {T}}\ HfO_{2}+2CO_{2}+2CO}},

{\ displaystyle {\ mathsf {Hf (C_ {2} O_ {4}) _ {2} \ {\ xrightarrow {T}} \ HfO_ {2} + 2CO_ {2} + 2CO}},}

{\mathsf {Hf(SO_{4})_{2}\ {\xrightarrow {T}}\ HfO_{2}+2SO_{3}}}.

{\ displaystyle {\ mathsf {Hf (SO_ {4}) _ {2} \ {\ xrightarrow {T}} \ HfO_ {2} + 2SO_ {3}}.}

Physical Properties

Hafnium (IV) oxide is a colorless crystals, in a finely dispersed state - a white powder, crystallizes in several crystalline modifications:

Monoclinic syngony , cell parameters a = 0.511 nm, b = 0.514 nm, c = 0.528 nm, β = 99.73 °, density 9.68 g / cm³, stable at temperatures below 1650 ° C.
The tetragonal syngony , cell parameters a = 0.514 nm, c = 0.525 nm, density 10.01 g / cm³, is stable at temperatures from 1650 ° С and up to ≈ 2500 ° С.
Cubic syngony , cell parameters a = 0.511 nm, density 10.43 g / cm ³, is stable at temperatures above ≈ 2500 ° С.

Does not dissolve in water, p PR = 63,94.

Chemical Properties

When precipitating from aqueous solutions, a precipitate of poorly soluble yellowish hydrate of the composition HfO ₂ · n H ₂ O is formed.

Calcined hafnium oxide is more chemically inert.

Hydrated form when heated decomposes to dihydroxide-hafnium oxide :

{\mathsf {HfO_{2}\cdot nH_{2}O\ {\xrightarrow {140-200^{o}C}}\ HfO(OH)_{2}+(n-1)H_{2}O}}.

{\ displaystyle {\ mathsf {HfO_ {2} \ cdot nH_ {2} O \ {\ xrightarrow {140-200 ^ {o} C}} \ HfO (OH) _ {2} + (n-1) H_ { 2} O}}.}

Slowly reacts with sulfuric acid :

{\mathsf {HfO_{2}+2H_{2}SO_{4}\ {\xrightarrow {\tau }}\ Hf(SO_{4})_{2}\downarrow +2H_{2}O}}.

{\ displaystyle {\ mathsf {HfO_ {2} + 2H_ {2} SO_ {4} \ {\ xrightarrow {\ tau}} \ Hf (SO_ {4}) _ {2} \ downarrow + 2H_ {2} O} }.}

Reacts with concentrated hydrofluoric acid :

{\mathsf {HfO_{2}+4HF\ {\xrightarrow {}}\ H_{2}[HfOF_{4}]+H_{2}O}}.

{\ displaystyle {\ mathsf {HfO_ {2} + 4HF \ {\ xrightarrow {}} \ H_ {2} [HfOF_ {4}] + H_ {2} O}}.}

Reacts with halogens in the presence of reducing agents :

{\mathsf {HfO_{2}+2Cl_{2}+C\ {\xrightarrow {500^{o}C}}\ HfCl_{4}+CO_{2}}}.

{\ displaystyle {\ mathsf {HfO_ {2} + 2Cl_ {2} + C \ {\ xrightarrow {500 ^ {o} C}} \ HfCl_ {4} + CO_ {2}}}.}

When fused with hydroxides, alkali metal oxides, it forms hafnium acid salts, hafnates :

{\mathsf {HfO_{2}+2NaOH\ {\xrightarrow {1000-1100^{o}C}}\ Na_{2}HfO_{3}+H_{2}O}}.

{\ displaystyle {\ mathsf {HfO_ {2} + 2NaOH \ {\ xrightarrow {1000-1100 ^ {o} C}} \ Na_ {2} HfO_ {3} + H_ {2} O}}.}

Application

For the manufacture of regulatory rods of nuclear reactors since hafnium has a high capture cross section for thermal neutrons .
As an anti-reflective coating of optical parts.
As a component of special glass and refractories .
As an additive to tungsten in the manufacture of filaments of electric lamps .
In microelectronics, it is used as a replacement of silicon oxide in the manufacture of MIS transistors due to the high coefficient of relative dielectric constant , which is 5–7 times higher than that of silicon dioxide , which was traditionally used as a gate dielectric ^[1] .
Allows you to diagnose and treat plaque with regular dental examination ^[2] .

Notes

↑ Intel . Intel's Fundamental Advance in Transistor Design Extends Moore's Law (Computing Performance )
↑ Alexander Dubov. Hafnium oxide nanoparticles will help detect and remove plaque (Unopened) . nplus1.ru. The appeal date is August 21, 2018.

Literature

Chemical Encyclopedia / Redkol .: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1988. - V. 1. - 623 p.
Chemist Handbook / Redcol .: B. P. Nikolsky et al. - 2nd ed., Rev. - M.-L.: Chemistry, 1966. - T. 1. - 1072 p.
Chemist Handbook / Redcol .: B. P. Nikolsky et al. - 3rd ed., Rev. - L .: Chemistry, 1971. - T. 2. - 1168 p.
Lidin, RA, et al. Chemical Properties of Inorganic Substances: Proc. manual for universities. - 3rd ed., Corr. - M .: Chemistry, 2000. - 480 p. - ISBN 5-7245-1163-0 .
Ripan R., Chetyanu I. Inorganic chemistry. Metal Chemistry. - M .: Mir, 1972. - T. 2. - 871 p.

[1] Intel . Intel's Fundamental Advance in Transistor Design Extends Moore's Law (Computing Performance )

[2] Alexander Dubov. Hafnium oxide nanoparticles will help detect and remove plaque (Unopened) . nplus1.ru. The appeal date is August 21, 2018.

Hafnium oxide

Are common
Systematic name	hafnium oxide (IV)
Traditional names	hafnium oxide
Chem. formula	HfO ₂
Physical properties
condition	white crystals
Molar mass	210.19 g / mol
Density	9.68 g / cm³
Thermal properties
T. melt.	2780; 2790 ° C
T. Kip.	5400 ° C
Mol heat capacity	60.2 J / (mol · K)
Education enthalpy	-1117 kJ / mol
Structure
Crystal structure	monoclinic, tetragonal, cubic
Classification
Reg. CAS number	12055-23-1
Pubchem
Reg. EINECS number
SMILES
Inchi
Chemspider
Security
NFPA 704	0 one 0