Aluminum nitride

Crystal structure
	__ Al 3+ __ N 3−
General
Surname	Aluminum nitride
Ratio formula	AlN
Brief description	white powdery solid
External identifiers / databases
EC number	246-140-8
ECHA InfoCard	100,041,931
PubChem	90455
ChemSpider	81668
Wikidata	Q414445
properties
Molar mass	40.99 g mol −1
Physical state	firmly
density	3.26 g cm −3
Melting point	> 2400 ° C (decomposition)
solubility	on contact with water gradual hydrolysis with formation of ammonia
safety instructions
H and P phrases	H: 372-410
	P: 260-280-301 + 330 + 331-303 + 361 + 353-305 + 351 + 338
Thermodynamic properties
ΔH f 0	−318.0 kJ / mol
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Aluminum nitride

Aluminum nitride , empirical formula AlN, is a chemical compound of aluminum and nitrogen . It belongs to the nitride class of materials and is a III-V compound semiconductor with a wide band gap . The band gap is at room temperature . ${\ displaystyle E _ {\ mathrm {Gap}} = 6 {,} 015 \, {\ text {eV}}}$

properties

Aluminum nitride is a white, flammable, but difficult to ignite, powdery solid with an ammonia-like odor that decomposes in water. It crystallizes in the wurtzite structure with the hexagonal space group P 6 ₃mc (space group no.186) . The aluminum atoms form a tight packing of spheres on a hexagonal lattice, the N atoms occupy half of the tetrahedral gaps in this lattice. The lattice constants are a = 311.14 pm and c = 497.92 pm. The X-ray density of AlN is 3.26 g / cm³. Aluminum and nitrogen are predominantly covalently bonded, the proportion of ionic bonding is 45%. The relative molecular mass M _r is 40.99 u. Under nitrogen atmosphere, it has a melting point of over 2200 ° C and a hardness on the Mohs scale of 9. From 2400 ° C decomposes the connection. Template: room group / 186

Aluminum nitride ceramic

Aluminum nitride is depressurized, usually at temperatures of about 1800 ° C sintered . With the help of suitable sintering additives, liquid phase sintering occurs. In practice, doping with calcium oxide and yttrium oxide has largely become the standard method.

AlN ceramic has a very high thermal conductivity of 180 W / (m · K). The use of AlN ceramics is therefore of interest where a lot of heat has to be dissipated, but the material must not be electrically conductive. AlN ceramic is mainly used as a substrate material in power electronics.

On an industrial scale, aluminum nitride is obtained as a thin film by physical deposition processes ( PVD ), sputtering or by organometallic chemical vapor deposition (MOCVD).

synthesis

Aluminum nitride powder can be produced from aluminum oxide , nitrogen or ammonia and carbon in excess at a temperature> 1600 ° C in a carbothermal reaction:

{\ displaystyle \ mathrm {2 \ Al_ {2} O_ {3} +9 \ C + 4 \ NH_ {3} \ longrightarrow 4 \ AlN + 3 \ CH_ {4} +6 \ CO}}

{\ displaystyle \ mathrm {Al_ {2} O_ {3} +3 \ C + N_ {2} \ longrightarrow 2 \ AlN + 3 \ CO}}

Another way is direct nitridation. With this type of synthesis, metallic aluminum or aluminum oxide powder is converted to AlN at temperatures> 900 ° C with N ₂ or NH ₃ :

{\ displaystyle \ mathrm {2 \ Al + N_ {2} \ longrightarrow 2 \ AlN}}

{\ displaystyle \ mathrm {Al_ {2} O_ {3} +2 \ NH_ {3} \ longrightarrow 2 \ AlN + 3 \ H_ {2} O}}

Responsiveness

Aluminum nitride powder is very sensitive to hydrolysis . Incomplete splitting of aluminum nitride into aluminum hydroxide and ammonia can be observed in the water . Sintered ceramic is not sensitive to hydrolysis. In caustic soda , aluminum nitride decomposes both as a powder and as a sintered ceramic to form ammonia and an aluminate solution according to:

{\ displaystyle \ mathrm {AlN + NaOH + 3 \ H_ {2} O \ longrightarrow NH_ {3} + Na [Al (OH) _ {4}]}}

Web links

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on aluminum nitride in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
↑ Data sheet Aluminum nitride at Sigma-Aldrich , accessed on January 25, 2020 ( PDF ).
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-5.
↑ J. Li, KB Nam, ML Nakarmi, JY Lin, and HX Jiang: Band structure and fundamental optical transitions in wurtzite AlN . In: Applied Physics Letters . tape 83 , no. 25 , 2003, p. 5163-5165 , doi : 10.1063 / 1.1633965 .
↑ Martin Feneberg, Robert AR Menschen, Benjamin Neuschl, Klaus Thonke, and Matthias Bickermann: High-excitation and high-resolution photoluminescence spectra of bulk AlN . In: Physical Review B . tape 82 , no. 7 , 2010, p. 075208 , doi : 10.1103 / PhysRevB.82.075208 .

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on aluminum nitride in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .

[sigma-2] Data sheet Aluminum nitride at Sigma-Aldrich , accessed on January 25, 2020 ( PDF ).

[CRC90_5_5-3] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-5.

[4] J. Li, KB Nam, ML Nakarmi, JY Lin, and HX Jiang: Band structure and fundamental optical transitions in wurtzite AlN . In: Applied Physics Letters . tape 83 , no. 25 , 2003, p. 5163-5165 , doi : 10.1063 / 1.1633965 .

[5] Martin Feneberg, Robert AR Menschen, Benjamin Neuschl, Klaus Thonke, and Matthias Bickermann: High-excitation and high-resolution photoluminescence spectra of bulk AlN . In: Physical Review B . tape 82 , no. 7 , 2010, p. 075208 , doi : 10.1103 / PhysRevB.82.075208 .