What is Zirconium
Zirconium (pronunciation: zer-KO-nee-em) is a hard, silvery-gray element that belongs to the group of transition metals and is represented by the chemical symbol Zr [1, 2, 3]. It is a malleable and ductile metallic element that can readily react with other elements to form stable compounds .
Isotopes of Zirconium
Zirconium has four stable, naturally occurring isotopes, including 90Zr, 91Zr, 92Zr, and 94Zr with a natural abundance of 51.45%, 11.22%, 17.15%, and 17.38% respectively . There are roughly 29 radioisotopes out of which the two most stable are 96Zr and 93Zr with half-lives of about 2.0 X 1019 years and 1.53 million years respectively .
Where is Zirconium Found
Zirconium is naturally found in several mineral species, mainly in zircon (zirconium silicate or ZrSiO4) and baddeleyite (zirconium dioxide or zirconia or ZrO2) [1, 2]. The metal is commercially isolated from zircon by first converting it to zirconium chloride and then through magnesium reduction of chloride . The top 3 zirconium reserve holding countries are Australia, South Africa, and Ukraine while the top 3 producers are Australia, South Africa, and China .
Origin of its Name: The element is named from the Arabic word ‘zargun’, which means ‘gold-colored’ .
Who discovered it: Zirconium was discovered by the German chemist Martin Heinrich Klaproth .
When and How was it Discovered
In the ancient times, gemstones containing zirconium were known as zircon . Martin Klaproth, in 1789, investigated zircon and separated the new element in the form of baddeleyite or zirconia, the oxide of zirconium .
Klaproth could not successfully isolate the pure metal while Humphry Davy was also unsuccessful in splitting zirconia through electrolysis in 1808 [1, 5]. In 1824, the Swedish chemist Jöns Jacob Berzelius isolated zirconium in black, powdery form by heating potassium hexafluorozirconate with potassium .
However, the entirely pure form was not produced until 1925 when the Dutch chemists Jan Hendrik de Boer and Anton Eduard van Arkel decomposed zirconium tetraiodide (ZrI4) . Today, the metal is manufactured in bulk through reduction of ZrI4 by magnesium .
|Atomic number||40 |
|CAS number||7440-67-7 |
|Position in the periodic table||Group||Period||Block|
|4 ||5 ||d |
Properties and Characteristics of Zirconium
|Relative atomic mass||91.224 |
|Atomic mass||91.224 amu |
|Molar mass||91.2240 g/mol |
|Color||Silvery, grayish-white [1, 5]|
|Melting point/freezing point||1854 °C, 3369 °F |
|Boiling point||4406 °C, 7963 °F |
|Density||6.52 g cm-3 |
|State of matter at room temperature (solid/liquid/gas)||Solid [1, 5]|
|– Brinell||650 MPa |
|– Mohs||5 |
|– Vickers||904 MPa |
|Electrical Conductivity||2.4 X 106 S/m |
|Thermal (heat) conductivity||23 W/(m K) |
|Specific heat||278 J kg-1 K-1 |
|Bulk modulus||Unknown |
|Shear modulus||Unknown |
|Young’s modulus||Unknown |
|– Temperature (K)||400||600||800||1000||1200||1400||1600||1800||2000||2200||2400|
|– Pressure (Pa)||–||–||–||–||–||1.05 X 10-10||6.17 X 10-8||8.68 X 10-6||0.45 X 10-3||0.011||0.155|
|Oxidation states||4 |
|Isotopes||Isotope||Mass||Abundance (%)||Half-life||Mode of decay|
|94Zr||93.906||17.38||> 1017 y||β-β-|
|96Zr||95.908||2.8||2.3 X 1019 y||β-β-|
|> 1.7 X 1018 y||β-|
Atomic Data of Zirconium (Element 40)
|Valence electrons||4 |
|– n||4 |
|– ℓ||2 |
|– mℓ||-1 |
|– ms||+1/2 |
|Electron configuration (noble gas configuration)||[Kr] 4d25s2 |
|– Number of electrons||40 |
|– Number of neutrons||51 |
|– Number of protons||40 |
|Radius of Atom|
|– Atomic radius||2.23 Å |
|– Covalent radius||1.64 Å |
|Electronegativity (Pauling-scale)||1.33 |
|Electron affinity||41.103 |
|Ionization energy (kJ mol-1)||1st||2nd||3rd||4th||5th||6th||7th||8th|
What is it Used for
- Since it is not good at absorbing neutrons, it is used to provide the outer covering for the fuel rods in nuclear reactors [1, 5]. The reactors in nuclear power stations can have over 100,000 meters of zirconium tubing .
- Being superconductive at low temperatures, the alloy of zirconium and niobium is used for making superconducting magnets [1, 5].
- Zirconium(IV) oxide is used to make ultra-strong ceramics, which can be used for manufacturing crucibles, furnace linings, abrasives, and foundry bricks because of its heat-resistant properties . It is used in antiperspirants, cosmetics, microwave filters, and food packaging industries .
- The natural gemstone zircon is available in various colors, out of which the most desirable is the golden one that is used for making jewelry . The colorless, cubic zirconia is used as a synthetic gemstone, and when cut, it resembles a diamond .
- Since zirconium is exceptionally resistant to corrosion, it is useful in corrosive environments, and its alloys are found in heat exchangers, pipes, and fittings .
- Zirconium silicate mixed with praseodymium or vanadium produces yellow and blue pigments for painting pottery .
- Porcelain veneered zirconium crowns, implant dentures, and bridges are used for replacing lost teeth .
- Since zirconium powder can naturally ignite in air, it may be used in explosive devices .
Zirconium is known to have low toxicity, and if exposed, people may experience irritation of skin and eyes . If inhaled, it can cause the formation of tumors in the lungs . It is not known to play any biological role .
- It is reported that over 1.5 million tons of zircon are mined annually, mainly in South Africa and Australia .
- Zirconium is graphically represented as a scarab beetle because zircon gemstones were used in jewelry by the ancient Egyptians who related scarab beetles with creation, transformation, and regeneration .
- The element is so strong that it can be used for producing knives and scissors .
The price of pure zirconium is about $1.57 per gram, and in bulk, it costs roughly $0.16 per gram .