Lithium niobate

Trigonal

A = 515 pm c = 1386 pm

Li (6 6), Nb, O (4 2)

Lithium niobium oxide

Off-white, odorless solid

Fixed

4.64 g · cm -3

1275 ° C

8000 mg · kg -1 ( LD50, rat, oral)

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Lithium niobate is a chemical compound having the formula LiNbO3. It is a transparent, crystalline solid which does not occur in nature. Lithium niobate be drawn (a mixture of lithium and niobium ( V) oxide ) commonly by the Czochralski method from a melt. Because of its crystal structure, it has a number of industrially useful properties, especially as the material in the non-linear optics.

Crystal structure

Lithium niobate crystallizes in the trigonal crystal system in the space group (H, in this case stands for the hexagonal setting of the unit cell ) 515 pm and c = 1386 pm and six formula units per unit cell with lattice parameters a =. The Nb5 cations are each surrounded by six oxygen atoms in the form of distorted octahedrons. This [ NbO6 ] link via common vertices to a three-dimensional network. In the gaps of the network are the Li cations which are in turn surrounded by twelve oxygen atoms. The coordination number of 12 can be described as 6 6, since six of the oxygen atoms have a significantly greater distance from lithium. As coordination polyhedra obtained for lithium a strongly distorted anticuboctahedron.

Physical Properties

Lithium niobate crystallizes as a colorless solid with a wide transparency range starting in the near UV to the mid-IR region corresponding to wavelengths of 320-5600 nm lithium niobate is birefringent and has at 633 nm refractive indices of no = 2.286 and ne = 2.202.

The crystals have a Mohs hardness of 5, lithium shows a number of physical effects: the stoichiometric composition ( LiNbO3 ) is below the Curie temperature Tc of 1213 ° C ( 1486 K), ferroelectric and thus nonlinear optical, electro-optical, photorefractive, elastooptisch, piezoelectric and pyroelectric. The ferroelectric Curie temperature depends on the composition, it is for the congruent composition (prepared from 48.45 % Li2O, 51.55% Nb2O5 ) 1143 ° C ( 1416 K). Above the Curie temperature, the material loses its ferroelectric properties and is in the paraelectric phase (space group ) on.

Nanoparticles

Nanoparticles are prepared by impregnation of the lithium niobate of porous carriers with solutions of metal salts followed by calcination and dissolution of the support matrix, or by a hydrothermal process. Spherical nanoparticles with a diameter of 10 nm 2 and subsequent ten-minute heating are produced in an infrared furnace by impregnation of a mesoporous silicate matrix with an aqueous solution of LiNO 3 and NH4NbO ( C2O4 ).

Areas of application

  • Interdigital transducer and, based on
  • Bandpass filter ( SAW filter ), in high-frequency circuits, such as mobile phones and televisions
  • Laser
  • Modulators
  • Integrated Optics
  • Holography

Similar compounds

The lithium tantalate LiTaO3 crystallizes isotypic to LiNbO3, which means it has the same crystal structure

Lattice constant CAS registry number Nonlinear optics Coordination geometry Pockels effect Photorefractive effect Interdigitaltransducer Digital Object Identifier
513418
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