Potassium niobate

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Crystal structure
Structure of potassium niobate
__ K +      __ Nb 5+      __ O 2−
General
Surname Potassium niobate
other names

Potassium metaniobate

Ratio formula KNbO 3
Brief description

orthorhombic crystals

External identifiers / databases
CAS number 12030-85-2
EC number 234-744-4
ECHA InfoCard 100,031,573
Wikidata Q1631815
properties
Molar mass 180.01 g mol −1
Physical state

firmly

density

4.62 g cm −3

Melting point

≈ 1100 ° C

solubility

almost insoluble in water

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: 312
Toxicological data

3000 mg kg −1 ( LD 50 ,  rat ,  oral )

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium niobate is a chemical compound made up of potassium , niobium and oxygen which is used as a single crystal in laser technology and for non-linear optical systems .

Extraction and presentation

Potassium niobate single crystals can be grown in crystal growing systems from melts of potassium niobate, which analytically consist of niobium (V) oxide and potassium oxide in a slight excess. Before this, potassium niobate is produced by melting together potassium carbonate and niobium (V) oxide. When the single crystals cool below about 435 ° C, the transition from the cubic to the ferroelectric, tetragonal modification takes place. Below about 220 ° C, the rhombic structure is stable with many (12 possible) different crystallographic orientations ( domains ).

properties

Physical Properties

Potassium niobate crystals have an orthorhombic distorted perovskite structure with the lattice parameters a = 569.7 pm, b = 397.1 pm and c = 572.2 pm. They have ferroelectric properties and a Mohs hardness of 5. Potassium niobate has the largest nonlinear optical coefficient of all commercially available inorganic crystals and is birefringent. For this reason the connection is used in lasers for frequency doubling and other optical processes. It is transparent in the wavelength range from 400 to 4500 nm . Its refractive index depends on the wavelength and the direction of light incidence in the crystal and is ≈2.2 (2.12 at 1064 nm in the x-direction and 2.38 at 532 nm in the z-direction). Since it changes its crystal structure at −50 ° C, 200 ° C and 430 ° C, the crystal must be kept in the temperature range between −40 and +200 ° C for optical purposes. In addition, the crystal has a piezoelectric effect , which means that it can be used as an ultrasound source.

use

Monocrystalline nanowires made from potassium niobate are used in near-field microscopy as an illumination source (generated by doubling the frequency from infrared to green light). In laser technology and non-linear optics , potassium niobate is used, for example, for frequency doubling, as a medium for optical parametric oscillators and others. It is used as an ultrasound source in acoustics.

See also

Individual evidence

  1. ↑ a b c Potassium Niobate Crystal. KNbO 3 . ( Memento from July 29, 2013 in the web archive archive.today ) Data sheet at Photox Optical Systems.
  2. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Inorganic Compounds, pp. 4-83.
  3. ↑ a b c data sheet potassium niobate from AlfaAesar, accessed on January 15, 2013 ( PDF )(JavaScript required) .
  4. ↑ Safety data sheet Potassium Niobate ( Memento from September 29, 2007 in the Internet Archive ) from Sigma-Aldrich, from March 18, 2004.
  5. ↑ PatentOnline: Process for the production of a potassium niobate single crystal
  6. ↑ University of Osnabrück: Cultivation of KNbO3 and KTa 1-x Nb x O 3 crystals ( Memento from September 8, 2006 in the Internet Archive ) (PDF; 597 kB)
  7. ↑ optical-components.com: KNbO3 Crystal ( Memento from August 18, 2007 in the Internet Archive )
  8. ↑ ii-vi.de: KNbO 3 ( Memento from January 14, 2011 in the Internet Archive )
  9. ↑ A. Radoua, D. Khatib: Theoretical study of photorefractive effect in reduced potassium niobate crystals. ( Memento from November 1, 2013 in the Internet Archive ) (PDF; 146 kB) Laboratoire de Physique du Solide Théorique, Département de Physique, Faculté des Sciences, BP: 28 / S, Université Ibn Zohr, 80000 Agadir, Maroc
  10. ^ Preparation of Potassium Niobate Single-Domain Crystals and Their Piezoelectric Properties. In: Ferroelectrics. Volume 292, Issue 1.
  11. ↑ Electroceramics in Japan VIII. Accessed May 5, 2019 (English).
  12. ^ S. Wada, K. Muraoka, H. Kakemoto, T. Tsurumi: Piezoelectric Properties of Potassium Niobate Single Crystals by Domain Engineering. In: Journal of the Korean Physical Society. Vol. 46, no. 1, January 2005, pp. 73-76.
  13. ↑ pro-physik.de: Nano-lamp for near-field microscopes

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