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{{chembox
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| verifiedrevid = 476994790
| ImageFile = Linbo3 Unit Cell.png
| ImageSize = 150px
| ImageFile2 =
| IUPACName =
| OtherNames =
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 10605804
| InChI = 1/Li.Nb.3O/q+1;;;;-1/rLi.NbO3/c;2-1(3)4/q+1;-1
| InChIKey = GQYHUHYESMUTHG-YHKBGIKBAK
| SMILES = [Li+].[O-][Nb](=O)=O
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Li.Nb.3O/q+1;;;;-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = GQYHUHYESMUTHG-UHFFFAOYSA-N
| CASNo = 12031-63-9
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 159404
}}
| Section2 = {{Chembox Properties
| Formula = LiNbO<sub>3</sub>
| MolarMass = 147.846 g/mol
| Appearance = colorless solid
| Density = 4.65 g/cm<sup>3</sup> <ref name=CT>[http://www.crystaltechnology.com/docs/LN_LTAppNote.pdf Spec sheet] of Crystal Technology, Inc.</ref>
| MeltingPt = 1257 °C<ref name="CT" />
| BoilingPt =
| Solubility = None
| SolubleOther =
| RefractIndex = n<sub>o</sub> 2.30, n<sub>e</sub> 2.21<ref>{{cite web |url=http://www.luxpop.com |title=Luxpop |accessdate= June 18, 2010}} (Value at ''n''<sub>D</sub>=589.2&nbsp;nm, 25&nbsp;°C.)</ref>
| BandGap = 4 eV
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[trigonal]]
| SpaceGroup = R3c
| PointGroup = 3m (C<sub>3v</sub>)
| Coordination =
| Dipole =
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf =
| DeltaHc =
| Entropy =
| HeatCapacity =
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| EUIndex = Not listed
| MainHazards =
| NFPA-H =
| NFPA-F =
| NFPA-R =
| NFPA-O =
| FlashPt =
}}
| Section8 = {{Chembox Related
| OtherAnions =
| OtherCations =
| OtherCpds =
}}
}}
 
'''Lithium niobate''' ({{Lithium}}{{Niobium}}{{Oxygen|3}}) is a compound of [[niobium]], [[lithium]], and [[oxygen]]. Its single crystals are an important material for optical waveguides, mobile phones, piezoelectric sensors, optical modulators and various other linear and non-linear optical applications.
 
==Properties==
Lithium niobate is a colorless solid insoluble in water. It has a [[trigonal]] [[crystal system]], which lacks [[inversion symmetry]] and displays [[ferroelectricity]], [[Pockels effect]], [[piezoelectric]] effect, [[photoelasticity]] and [[nonlinear optics|nonlinear optical]] polarizability. Lithium niobate has negative uniaxial [[birefringence]] which depends slightly on the [[stoichiometry]] of the crystal and on temperature. It is transparent for wavelengths between 350 and 5200 [[nanometer]]s.
 
Lithium niobate can be doped by [[magnesium oxide]], which increases its resistance to optical damage (also known as photorefractive damage) when doped above the [[optical damage threshold]]. Other available dopants are {{iron}}, {{zinc}}, {{hafnium}}, {{copper}}, {{gadolinium}}, {{erbium}}, {{yttrium}}, {{Manganese}} and {{boron}}.
 
==Growth==
[[Single crystal]]s of lithium niobate can be grown using the [[Czochralski process]].<ref>{{cite book|title = Lithium Niobate: Defects, Photorefraction and Ferroelectric Switching|first = Tatyana|last = Volk|coauthors = Wohlecke, Manfred|publisher = Springer|year = 2008|isbn = 978-3-540-70765-3|doi=10.1007/978-3-540-70766-0|pages=1–9}}</ref> [[File:Lithium Niobate Wafer.jpg|175px|thumb|A Z-cut, single crystal Lithium Niobate wafer|left]] After a crystal is grown, it is sliced into wafers of different orientation. Common orientations are Z-cut, X-cut, Y-cut, and cuts with rotated angles of the previous axes.<ref>{{cite book|last=Wong|first=K. K.|title=Properties of Lithium Niobate|year=2002|publisher=INSPEC|location=London, United Kingdom|isbn=0 85296 799 3|pages=8}}</ref>
 
==Nanoparticles==
Nanoparticles of lithium niobate and [[niobium pentoxide]] can be produced at low temperature.<ref>{{cite journal|author = Grange, R.; Choi, J.W.; Hsieh, C.L.; Pu, Y.; Magrez, A.; Smajda, R.; Forro, L.; Psaltis, D. |title = Lithium niobate nanowires: synthesis, optical properties and manipulation |journal = Applied Physics Letters|volume = 95|pages =  143105|year = 2009|url =http://link.aip.org/link/?APPLAB/95/143105/1}}</ref> The complete protocol implies a LiH induced reduction of NbCl<sub>5</sub> followed by ''in situ'' spontaneous oxidation into low-valence niobium nano-oxides. These niobium oxides are exposed to air atmosphere resulting in pure Nb<sub>2</sub>O<sub>5</sub>. Finally, the stable Nb<sub>2</sub>O<sub>5</sub> is converted into lithium niobate LiNbO<sub>3</sub> nanoparticles during the controlled hydrolysis of the LiH excess.<ref>{{cite journal|author = Aufray M, Menuel S, Fort Y, Eschbach J, Rouxel D, Vincent B|title = New Synthesis of Nanosized Niobium Oxides and Lithium Niobate Particles and Their Characterization by XPS Analysis|journal = Journal of Nanoscience and Nanotechnology|volume = 9|issue = 8|pages = 4780–4789|year = 2009|doi = 10.1166/jnn.2009.1087}}</ref> Spherical nanoparticles of lithium niobate with a diameter of approximately 10&nbsp;nm can be prepared by impregnating a mesoporous silica matrix with a mixture of an aqueous solution of LiNO<sub>3</sub> and NH<sub>4</sub>NbO(C<sub>2</sub>O<sub>4</sub>)<sub>2</sub> followed by 10 min heating in an IR furnace.<ref>{{cite journal|author = Grigas, A; Kaskel, S |title = Synthesis of LiNbO<sub>3</sub> nanoparticles in a mesoporous matrix |journal = Beilstein Journal of Nanotechnology|volume = 2|pages = 28–33|year = 2011|doi =10.3762/bjnano.2.3}}</ref>
 
==Applications==
Lithium niobate is used extensively in the telecoms market, e.g. in [[mobile telephone]]s and [[optical modulator]]s. It is the material of choice for the manufacture of [[surface acoustic wave]] devices. For some uses it can be replaced by [[lithium tantalate]], {{lithium}}{{tantalum}}{{oxygen|3}}. Other uses are in [[laser]] [[second harmonic generation|frequency doubling]], [[nonlinear optics]], [[Pockels effect#Pockels cells|Pockels cell]]s, [[optical parametric oscillator]]s, [[Q-switching]] devices for lasers, other [[acousto-optic effect|acousto-optic]] devices, [[optical switch]]es for gigahertz frequencies, etc. It is an excellent material for manufacture of [[optical waveguide]]s.
 
It's also used in the making of optical spatial low-pass ([[Anti-aliasing_filter|anti-aliasing]]) filters.
 
==Periodically poled lithium niobate (PPLN)==
'''Periodically poled lithium niobate''' ('''PPLN''') is a domain-engineered lithium niobate crystal, used mainly for achieving [[quasi-phase-matching]] in [[nonlinear optics]]. The [[ferroelectric]] domains point alternatively to the ''+c'' and the ''-c'' direction, with a period of typically between 5 and 35 [[micrometre|µm]]. The shorter periods of this range are used for [[second harmonic generation]], while the longer ones for [[Optical parametric oscillator|optical parametric oscillation]]. [[Periodic poling]] can be achieved by electrical poling with periodically structured electrode. Controlled heating of the crystal can be used to fine-tune [[phase matching]] in the medium due to a slight variation of the dispersion with temperature.
 
Periodic poling uses the largest value of lithium niobate's nonlinear tensor, d<sub>33</sub>= 27 pm/V. Quasi-phase matching gives maximum efficiencies that are 2/π (64%) of the full d<sub>33</sub>, about 17 pm/V
 
Other materials used for [[periodic poling]] are wide [[band gap]] inorganic crystals like [[potassium titanyl phosphate|KTP]] (resulting in [[periodically poled KTP]], [[PPKTP]]), [[lithium tantalate]], and some organic materials.
 
The periodic poling technique can also be used to form surface [[nanostructure]]s.<ref>{{cite journal |title=Surface nanoscale periodic structures in congruent lithium niobate by domain reversal patterning and differential etching |author=S. Grilli |coauthors=P. Ferraro, P. De Natale, B. Tiribilli, and M. Vassalli |journal=Applied Physics Letters |volume=87 |issue=23 |pages=233106 |year=2005 |doi=10.1063/1.2137877}}</ref><ref>{{cite journal |title=Modulating the thickness of the resist pattern for controlling size and depth of submicron reversed domains in lithium niobate
|author=P. Ferraro |coauthors=S. Grilli |journal=Applied Physics Letters |volume=89 |issue=13 |pages=133111 |year=2006 |doi=10.1063/1.2357928}}</ref>
 
However, due to its low photorefractive damage threshold, PPLN only finds limited applications: at very low power levels. MgO doped lithium niobate is fabricated by periodically poled method. Periodically poled MgO doped lithium niobate (PPMgOLN) therefore expands the application to medium power level.
 
==Sellmeier equations==
The [[Sellmeier equation]]s for the extraordinary index are used to find the poling period and approximate temperature for quasi-phase matching. Jundt<ref name=Jundt>{{cite journal| author=Dieter H. Jundt| journal=Optics Letters|volume=22 |title=Temperature-dependent Sellmeier equation for the index of refraction <math>n_e</math> in congruent lithium niobate| year=1997|pages=1553–5 |doi=10.1364/OL.22.001553| pmid=18188296| issue=20}}</ref> gives
 
<math>n^2_e =
5.35583 + 4.629 \times 10^{-7} f
+ {0.100473 + 3.862 \times 10^{-8} f \over \lambda^2 - (0.20692 - 0.89 \times 10^{-8} f)^2 }
+ { 100 + 2.657 \times 10^{-5} f \over \lambda^2 - (11.34927 )^2 }
- 1.5334 \times 10^{-2} \lambda^2 </math>
 
valid from 20-250 °C for wavelengths from 0.4 to 5 [[micrometre|micrometer]]s, whereas for longer wavelength,<ref name=Deng>{{cite journal|author=LH Deng et al.|journal = Optics Communications|volume=268| title=Improvement to Sellmeier equation for periodically poled LiNbO<math>_3</math> crystal using mid-infrared difference-frequency generation|issue=1|year=2006| pages=110|doi=10.1016/j.optcom.2006.06.082}}</ref>
 
<math>n^2_e =
5.39121 + 4.968 \times 10^{-7} f
+ {0.100473 + 3.862 \times 10^{-8} f \over \lambda^2 - (0.20692 - 0.89 \times 10^{-8} f)^2 }
+ { 100 + 2.657 \times 10^{-5} f \over \lambda^2 - (11.34927 )^2 }- (1.544 \times 10^{-2} + 9.62119 \times 10^{-10} \lambda) \lambda^2 </math>
 
which is valid for ''T'' = 25 to 180 °C, for wavelengths λ between 2.8 and 4.8 micrometers.<br>
In these equations f = (T-24.5)(T+570.82), λ is in micrometers, and T is in °C.
 
==See also==
<!-- alphabetic order -->
{{colbegin|3}}
*[[Crystal]]
*[[Crystal structure]]
*[[Crystallite]]
*[[Crystallization]] and [[Crystallization (engineering aspects)|engineering aspects]]
*[[Seed crystal]]
*[[Single crystal]]
*[[Laser-heated pedestal growth]]
*[[Micro-Pulling-Down]]
{{colend}}
 
==References==
{{reflist|2}}
 
==Further reading==
*{{cite book|title=Ferroelectric Crystals for Photonic Applications Including Nanoscale Fabrication and Characterization Techniques |series=Springer Series in Materials Science |volume= 91 |editor-last=Ferraro |editor-first=Pietro |editor2-last=Grilli |editor2-first=Simonetta |editor3-last=De Natale |editor3-first=Paolo |url=http://www.springer.com/materials/book/978-3-540-77963-6|doi=10.1007/978-3-540-77965-0}}
 
==External links==
*[http://www.inrad.com/pdf/Inrad_datasheet_LNB.pdf Inrad data sheet on lithium niobate]
 
{{Lithium compounds}}
 
[[Category:Lithium compounds]]
[[Category:Niobates]]
[[Category:Ferroelectric materials]]
[[Category:Nonlinear optical materials]]
[[Category:Crystals]]
[[Category:Second-harmonic generation]]

Revision as of 00:00, 16 February 2014

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