Nitride

As nitrides is called the chemical compounds of nitrogen (Latin: Nitrogenium ) with another, less electronegative element. The nitrogen in these compounds is formally a triple negative charge ( oxidation number ) awarded ( N3: nitride anion). Nitrides can be classified according to the character of the prevailing type of bond. From ionic ( salt-like ) nitrides occurs when the binding partner is a strongly electropositive metal such as lithium in the lithium nitride. Metal nitrides are often formed with transition metals, such as the various iron nitrides. In the case of non-metals or semi-metals as a binding partner to form mostly predominantly covalently bonded, three-dimensional solids such as aluminum nitride or - more rarely - typical molecular compounds such as ammonia ( " Wasserstoffnitrid " ), as its salts or derivatives ( derivatives) the nitrides can be considered.

The nitrides are not to be confused with nitrites (NO2 - ), the salts of nitrous acid.

• 3.1 Minerals

Examples

Covalent nitrides

Covalent nitrides are partly diamond-like (example: boron nitride), some of them very reactive and unstable (example: Jodstickstoff ). However, boron nitride can be chemically converted, eg to Jodstickstoff - for the first time in 1990 of boron nitride and iodine fluoride in trichlorofluoromethane at -30 ° C.

Covalent nitrides caused the elements of the 3rd to 5th main groups. Important covalent nitrides besides boron nitride ( BN) with elements of the third main group of aluminum nitride ( AlN) and gallium nitride (GaN ) and indium nitride ( InN ). With elements of the fourth main group to form carbon nitride ( C3N4, the subject of current research, theory, harder than diamond ), silicon nitride ( Si3N4, for high-strength, high temperature resistant technical ceramics ), germanium ( Ge3N4 ), and tin ( IV ) nitride ( Sn3N4 ). Also, phosphorus nitride ( P3N5 ) is one of the covalent nitrides, as well as the more precious metals nitrides, for example: copper (I ) nitride ( Cu3N ).

Metal nitrides

Metal nitrides tend to be intercalated compounds ( such as interstitial alloys ) and very hard crystals form. You will der4 of the transition metals. formed to subgroup 8. As hard materials can be mentioned among others: titanium nitride ( TiN, in compensation layers on drills, milling cutters, carbide indexable inserts ), tantalum nitride (TaN ), chromium nitride ( CrN, remuneration of special tools made ​​of chrome ). In nitriding steels arise iron nitride phases as Fe4N and Fe3N1 x and nitrides of various alloying elements.

Ionic nitrides

Ionic nitrides are substances of salt-like character. They react with water and acids into ammonia gas and metal hydroxides, as the nitride ion is protonated (acid-base reaction). May be produced from ammonia, magnesium, for example: When the burning of magnesium powder magnesium nitride is formed as a yellow solid (for example, metallic magnesium by heating at about 600 ° C under nitrogen atmosphere instead of air ), the reaction scheme:

( The combustion of magnesium metal in air, it is created next to magnesium oxide ( MgO) and lets it appear yellowish). With water this salt-like magnesium nitride is then hydrolyzed to magnesium hydroxide and ammonia gas:

The group of salt-like, reacting well with water nitrides include Alkalinitride as lithium nitride ( Li 3 N ) and sodium nitrite ( Na3N ) to the Erdalkalinitriden Berylliumnitrid ( Be3N2, partially covalent), the above-mentioned magnesium nitride ( Mg3N2 ) and calcium nitride ( Ca3N2 ). Even with other electro-positive subgroup metals exist ionic nitrides, such as Zinknitrid ( Zn3N2 ), scandium nitride ( ScN ), yttrium nitride ( YN ), lanthanum nitride ( LaN ), zirconium (IV ) nitride ( Zr3N4 ), tantalum (V ) - nitride ( Ta3N5 ) Urannitride (UN, U2N3, UN2 ) and thorium (IV ) nitride ( Th3N4 ).

Use

Most used industrially nitrides are used for surface hardening. Thus one uses eg silicon nitride ( Si3N4) as an antireflection layer. Metal -like and the so-called diamond-like nitrides serve as hard materials, high-temperature and refractory ceramic materials, such as titanium nitride ( TiN).

Also nitrides are used in microelectronics. There, they find use as diffusion barriers (eg tantalum ) or passivation layers ( mainly silicon ).

Nitrides of elements of main group 3 ( AlN, GaN, InN ) have III -V semiconductor and used in electro-optic devices due to their large band gap for generating light with short wavelengths (blue). Requirement for function of white LEDs.

Occurrence of nitrides in nature

Minerals

Nitride minerals are extremely rare. You can only form under oxygen-free conditions. This results from the much higher reactivity of oxygen O2 ( " biradical " dissociation 498.67 kJ / mol ) compared to the nitrogen N2 ( triple bond dissociation enthalpy of 946.04 kJ / mol).

• Roaldit ( Fe4N )
• Siderazot ( Fe3N )
• Osbornit (TiN)
• Carlsbergit (CrN )
• Sinoite ( Si2ON2 )