Barium borate
Crystal structure | |||||||||||||||||||
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Crystal structure of β-barium borate __ Ba 2+ __ B 3+ __ O 2− |
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General | |||||||||||||||||||
Surname | Barium borate | ||||||||||||||||||
other names |
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Ratio formula | Ba (BO 2 ) 2 | ||||||||||||||||||
Brief description |
white odorless solid (monohydrate) |
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properties | |||||||||||||||||||
Molar mass | 222.95 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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density |
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Melting point |
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solubility |
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Refractive index |
1.55-1.60 (monohydrate) |
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safety instructions | |||||||||||||||||||
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Toxicological data | |||||||||||||||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C |
Barium borate (more precisely barium metaborate ) is a chemical compound of barium from the group of borates . It occurs in various modifications that are characterized by unusual properties such as optical birefringence and optical non-linearity .
Extraction and presentation
Barium borate can be obtained by reacting a boric acid solution with barium hydroxide . The γ-barium borate formed contains water of crystallization that can be removed by heating to 300-400 ° C. When heated to 600 to 800 ° C, this is completely converted to β-barium borate. Barium borate monohydrate is made from a solution of barium sulfide and sodium tetraborate . The dihydrate is formed by precipitation from a barium chloride solution by adding a sodium metaborate solution at 90 to 95 ° C. The tetrahydrate precipitates at room temperature.
properties
Barium borate monohydrate is a white solid that is not very soluble in water. The dihydrate, which is also white, loses water of crystallization at 140 ° C. The high-temperature form α-barium borate has good mechanical properties (Mohs hardness of 4.5), high birefringence and is transparent in a very wide range between 189 and 3500 nm. It crystallizes trigonal , space group R 3 c (space group no. 167) with the lattice parameters a = 7.235 Å and c = 39.19 Å. Similar to the α-form, the low-temperature form β-barium borate (BBO) has a trigonal crystal structure with the space group R 3 c (No. 161) and the lattice parameters a = 8.380 Å and α = 96.65 °. The structure contains almost planar trimeric ions (BO 2 ) 3 - . Each barium atom is coordinated by eight oxygen atoms from neighboring anions. The low temperature phase exhibits non-linear optical properties. Compared to potassium dihydrogen phosphate (KDP), the compound has almost six times as high a non-linearity and a wide range of wavelengths (approx. 210 to 2100 nm ) in which the crystal is transparent. Similar to KDP, BBO can also be used for laser pulses with a very high energy density (high damage threshold: approx. 5 GW / cm 2 at 1064 nm wavelength and 10 ns pulse duration).
The refractive indices n o and n e of BBO are given by the Sellmeier equation
described. Different values are given in publications for the experimentally determined Sellmeier coefficients ( A , B , C , D ). Exemplary the values of Kato:
A. B / µm 2 C / µm 2 D / µm −2 n o 2.7359 0.01878 −0.01822 −0.01354 n e 2.3753 0.01224 −0.01667 −0.01516
use
Barium borate monohydrate is used as a pigment , corrosion inhibitor (due to its alkaline properties), flame retardant , tannin discoloration blocking agent for paints and others. The dihydrate is used as a flame retardant in paint, paper, textiles and plastic. Barium borate has been approved as a bactericide and fungicide in the United States since the 1960s . α-barium borate is a useful material for high-performance UV light polarization optics and acousto-optics . β-barium borate is used for:
- Frequency doubling and mixing (generation of the sum and difference frequency ) of the light from (pulsed) lasers
- Correlation for measuring the pulse duration and shape of ultra-short laser pulses
- optical parametric oscillators
- Pockels cells
- to generate UV light
Related links
- Barium orthoborate Ba 3 (BO 3 ) 2
Individual evidence
- ↑ a b c d data sheet Barium metaborate monohydrate from AlfaAesar, accessed on June 8, 2014 ( PDF )(JavaScript required) .
- ↑ a b c d e Richard C. Ropp: Encyclopedia of the Alkaline Earth Compounds . Newnes, 2012, p. 511 ( limited preview in Google Book search).
- ↑ a b c d e W. Paulus: Microbicides for the Protection of Materials: A Handbook . Springer, 1993, p. 429 ( limited preview in Google Book search).
- ↑ a b Entry on barium metaborate in the GESTIS substance database of the IFA , accessed on July 23, 2016(JavaScript required) .
- ↑ a b Govindhan Dhanaraj, Kullaiah Byrappa, Vishwanath Prasad, Michael Dudley: Springer Handbook of Crystal Growth . Springer, 2010, p. 729 ff . ( limited preview in Google Book search).
- ^ A b c Dale L. Perry: Handbook of Inorganic Compounds, Second Edition . CRC Press, 2011, pp. 498 ( limited preview in Google Book search).
- ^ William M. Haynes: CRC Handbook of Chemistry and Physics, 93rd Edition . CRC Press, 2012, p. 50 ( limited preview in Google Book search).
- ↑ The designation of the low and high temperature forms as β and α forms is handled inconsistently in the literature. In the more recent literature, the designation α-form has established itself for the high-temperature form.
- ↑ A. Perloff, S. Block, AD Mighell: The crystal structure of the high temperature form of barium borate. In: Acta Crystallographica , 20, 1966, pp. 819-823, doi: 10.1107 / S0365110X66001920 .
- ↑ a b R. Fröhlich: Crystal structure of the low-temperature form of BaB 2 O 4 . In: Zeitschrift für Kristallographie , 168, 1984, pp. 109–112, doi: 10.1524 / zkri.1984.168.14.109 .
- ↑ K. Kato: "Second-Harmonic Generation to 2048 Å in β-BaB 2 O 4 ", IEEE Journal of Quantum Electronics , 1986, 22 (7), pp. 1013-1014, doi : 10.1109 / JQE.1986.1073097 .
- ^ Amy Forsgren: Corrosion Control Through Organic Coatings . CRC Press, 2006, pp. 42 ( limited preview in Google Book search).
- ↑ Michael Ash, Irene Ash: Handbook of Green Chemicals . Synapse Info Resources, 2004, p. 132 ( limited preview in Google Book search).
- ↑ I. Martynyuk-Lototska: Highly efficient acoustooptic diffraction in alpha-BaB2O4 crystals: improving of geometry of acoustooptic interaction. In: Ukrainian Journal of Physical Optics. 13, 2012, p. 28, doi : 10.3116 / 16091833/13/1/28/2012 .
- ↑ Mark Peltz: Characterization of new nonlinear crystals for frequency conversion ... Tenea Verlag Ltd., 2004, p. 148 ( limited preview in Google Book search).