Mixed anion compounds


Mixed anion compounds, heteroanionic materials or mixed anion materials are chemical compounds containing cations and more than one kind of anion. The compounds contain a single phase, rather than just a mixture.

Use in materials science

By having more than one anion, many more compounds can be made, and properties tuned to desirable values.
In terms of optics, properties include laser damage threshold, refractive index, birefringence, absorption particularly in the ultraviolet or near infrared, non-linearity.
Mechanical properties can include ability to grow a large crystal, ability to form a thin layer, strength, or brittleness.
Thermal properties can include melting point, thermal stability, phase transition temperatures, Thermal expansion coefficient.
For electrical properties, electric conductivity, band gap, superconducting transition temperature piezoelectricity, pyroelectricity, ferromagnetism, dielectric constant, charge-density wave transition can be adjusted.

Production

Many of the non-metals that could make mixed anion compounds may have greatly varying volatilities. This makes it more difficult to combine the elements together. Compounds may be produced in a solid state reaction, by heating solids together, either in a vacuum or a gas. Common gases used include, oxygen, hydrogen, ammonia, chlorine, fluorine, hydrogen sulfide, or carbon disulfide. Soft chemical approaches to manufacture include solvothermal synthesis, or substituting atoms in a structure by others, including by water, oxygen, fluorine or nitrogen. Teflon pouches can be used to separate different formulations. Thin film deposits can yield strained layers. High pressures can be used to prevent evaporation of volatiles. High pressure can reulst in different crystal forms, perhaps with higher coordination number.

Kinds

Elemental

HBCNOFSiPSClGeAsSeBrSbTeIBi
BBHBCBNBOBFBSiBPBSBClBGeBAsBSeBBrBSbBTeBIBBi
CCHCBCNCOCFCSiCPCSCClCGeCAsCSeCBrCSbCTeCICBi
NNHNBNCNONFNSiNPNSNClNGeNAsNSeNBrNSbNTeNINBi
OOHOBOCONOFOSiOPOSOClOGeOAsOSeOBrOSbOTeOIOBi
FFHFBFCFNFOFSiFPFSFClFGeFAsFSeFBrFSbFTeFIFBi
SiSiHSiBSiCSiNSiOSiFSiPSiSSiClSiGeSiAsSiSeSiBrSiAsSiTeSiISiBi
PPHPBPCPNPOPFPSiPSPClPGePAsPSePBrPSbPTePIPBi
SSHSBSCSNSOSFSSiSPSClSGeSAsSSeSBrSSbSTeSISBi
ClClHClBClCClNClOClFClSiClPClSClGeClAsClSeClBrClSbClTeBiIClBi
GeGeHGeBGeCGeNGeOGeFGeSiGePGeSGeClGeAsGeSeGeBrGeSbGeTeGeIGeBi
AsAsHAsBAsCAsNAsOAsFAsSiAsPAsSAsClAsGeAsSeAsBrAsSbAsTeAsIAsBi
SeSeHSeBSeCSeNSeOSeFSeSiSePSeSSeClSeGeSeAsSeBrSeSbSeTeSeISeBi
BrBrHBrBBrCBrNBrOBrFBrSiBrPBrSBrClBrGeBrAsBrSeBrSbBrTeBrIBrBi
SbSbHSbBSbCSbNSbOSbFSbSiSbPSbSSbClSbGeSbAsSbSeSbBrSbTeSbISbBi
TeTeHTeBTeCTeNTeOTeFTeSiTePTeSTeClTeGeTeAsTeSeTeBrTeSbTeITeBi
IIHIBICINIOIFISiIPISIClIGeIAsISeIBrISbITeIBi
BiBiHBiBBiCBiNBiOBiFBiSiBiPBiSBiClBiGeBiAsBiSeBiBrBiSbBiTeBiI

Molecular anions

Oligomers

Some pairs of elements can form several different anions, and compounds may exist with more than one. One example is the sulfite sulfates. These kinds also include different oligomeric forms such as phosphates or fluorotitanates

Organic