Sodium niobate
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| __ Na + __ Nb 5+ __ O 2− | |||||||||||||
| General | |||||||||||||
| Surname | Sodium niobate | ||||||||||||
| Ratio formula | NaNbO 3 | ||||||||||||
| Brief description |
White dust |
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| properties | |||||||||||||
| Molar mass | 163.89 g mol −1 | ||||||||||||
| Physical state |
firmly |
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| density |
4.55 g cm −3 |
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| Melting point |
1422 ° C |
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| solubility |
almost insoluble in water |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||
Sodium niobate , NaNbO 3 , is a chemical compound of sodium , niobium and oxygen , comparable to potassium niobate . The compound is water-insoluble and when cooled below -200 ° C ferroelectric .
properties
Sodium niobate crystallizes in a crystal structure comparable to perovskite . Different phase changes take place with temperature changes. A total of seven different phases at different temperatures are known. At room temperature, a monoclinic crystal structure with the lattice parameters a = 551 pm , b = 557 pm, c = 1552 pm and β = 89.94 ° is stable. Below −80 ° C, a rhombohedral structure is more stable, when heated above 370 ° C the structure changes into an orthorhombic crystal structure. After a further two phase transitions at 480 and 520 ° C, at which the orthorhombic cell is maintained, the crystal system at 575 ° C converts into a tetragonal to. The last phase change takes place at 640 ° C, above this temperature sodium niobate crystallizes in a cubic crystal structure.
Occurrence
Three of the modifications of sodium niobate could be detected as natural mineral formations . The orthorhombic modification is known as Lueshit , the cubic as Isolueshit and the trigonal as Pauloabibit . Another possible mineral is the monoclinic crystallizing natroniobite , the status of which, however, is still questionable.
Manufacturing
Sodium niobate can be obtained by solid or melt reaction of sodium carbonate or hydroxide with niobium (V) oxide .
use
Due to the strong expression of ferroelectric properties, a potassium-sodium niobate can be used to manufacture piezo actuators for automotive applications (common rail injectors). This is important because lead zirconate titanate (PZT) has been used for these so far and automobiles are to be produced without heavy metals in the future . Another advantage is the strongly pronounced d33 effect (expansion in the field direction, see piezo effect ) with approx. 300 pm / V.
See also
Individual evidence
- ↑ Sodium niobate data sheet (PDF) from Strem, accessed on December 25, 2012.
- ↑ a b c David R. Lide: CRC Handbook of Chemistry and Physics . 87th edition. Taylor & Francis, 2007, ISBN 978-0-8493-0488-0 .
- ↑ Sodium niobate data sheet from AlfaAesar, accessed on February 18, 2010 ( PDF )(JavaScript required) .
- ↑ a b Sodium niobate data sheet from Sigma-Aldrich , accessed on April 14, 2011 ( PDF ).
- ↑ Konrad Kopitzki, Peter Herzog: Introduction to Solid State Physics. 5th edition, Vieweg + Teubner Verlag, 2004, ISBN 3-519-43083-5 , p. 235.
- ↑ CNW Darlington, KS Knight: On the lattice parameters of sodium niobate at room temperature and above. In: Physica B: Condensed Matter. 1999, 266, 4, pp. 368-372, doi : 10.1016 / S0921-4526 (99) 00043-5 .
- ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: November 2018. (PDF 1753 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, November 2018, accessed March 17, 2018 .