Boreto

Em química um boreto é um composto entre o elemento boro e um elemento menos eletronegativo.[1] É um grupo muito grande de compostos que são geralmente de ponto de fusão alto e não iônicos na natureza. Alguns boretos exibem propriedades físicas muito úteis, como alta dureza. O termo boreto é também livremente aplicado para compostos como B12As2 (Nota: o arsênio tem uma eletronegatividade mais alta que o boro) que é frequentemente citado como boreto icosaédrico.

Variedades de compostos

Os boretos podem ser classificados sem rigor como ricos em boro rico ou ricos em metal, por exemplo, o composto YB66 em um extremo até Nd2Fe14B no outro. A definição geralmente aceita é que se a proporção de átomos de boro de átomos de metal é 4:1 ou mais o composto é rico em boro, se é menor, então é rico em metal.

Boretos ricos em boro (B:M 4:1 ou mais)

Os principais grupos de metais, lantanídeos e actinídeos formam uma larga variedade de boretos ricos em boro, com razões metal:boro até YB66.

As propriedades deste grupo variam de um composto para o próximo, e incluem examplos de compostos que são semicondutores, supercondutores, diamagnéticos, paramagnético, ferromagneéticos ou anti-ferromagnético.[2] Eles são principalmente estáveis ​​e refratários.

Referências

  1. ↑ International Union of Pure and Applied Chemistry, Nomenclature of Inorganic Chemistry, Second Edition (1970), Systematic Names [em linha]
  2. ↑ Lundstrom T (1985). «Structure, defects and properties of some refractory borides». Pure & Applied Chem (free download pdf). 57 (10): 1383. doi:10.1351/pac198557101383 

Bibliografia

  • Greenwood, Norman N.; Earnshaw, Alan. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419
  • Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5

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