Boride carbides, borocarbides or carboborides are chemical compounds composed of metal along with boride and carbide anions. They are mostly metallic in nature, strong, resistant to heat, and some are superconductors.

Boride carbides form crystalline ceramics of a wide range of composition. They have been called "a toy box for solid state physicists".

Four structure classes exist based on the dimensionality of the carbon-boron structure. One category has metal atoms embedded in a 3D-net of boron-carbon. Also there are those with a two-dimensional network of boron and carbon, alternating with sheets of metal atoms. Thirdly are those with a one-dimensional boron-carbon structure embedded in channels in the metal. Lastly there are zero-dimensional molecular-like carbon-boron structures embedded in holes in the metal. Substances with B2C2 can be termed diborodicarbides. An example series of 2D materials is (RC)m(Ni2B2)n with R a rare earth, has layers of RC alongside NiB layers.

In the zero-dimensional case, dicarbidoborate [BC2]5− or CBC5− or CBC7− can exist isoelectronic with azides and cyanates. Other finite chain structures exist like [BC3]5− [B2C2]6− [B2C4]6− [B3C3]7− [B4C4]8− [B4C7]8− [B5C8]9− [B5C5]9− (C2−=B−=C=B−=B−=C=B−=C=B−=C2−) [B5C6]9−

Additional carbon ions may be in the form of C4− [C2]2− [C2]4− [C2]6− or [C3]4− Carbidonitridoborate CBN4− also can be made if nitrogen is present. As of 2024, [OBC]3− or [NCB]4− have not been discovered.

Boride carbides are formed by melting together elements, or carbides and borides.

Hydrogen can be absorbed without changing the structure as in YNi2B2CH0.2. Some compounds also contain halogens, which are not bound to carbon or boron, being found as independent ions.

Due to their extremely high melting point and ability to retain strength when heated, boride carbides are under investigation for use in ultra-high temperature applications, such as in supersonic vehicles. The 3D varieties are under consideration as high temperature superconductors. Some of these compounds are under investigation for thermoelectric applications.

List formulaspace groupunit cellremarksrefLiBCLiBC3Pm2a = 2.4588 c = 6.770metallic greyLiB2C2P63/mmca = 2.5930 c = 22.680t-LiB2C2Pm2a=4.1389 c=7.1055 Z=2o-LiB13C2Immaa = 5.668 b = 10.820 c = 8.040colourless; acid stable; B122− and CBC+; band gap 3.32 eVr-Li~1B13C2Rma = 5.6535 c = 12.5320transparentLi2B2CLi2B12C2Amm2a = 4.706 b = 9.010 c = 5.65 Z = 2 pale greenish yellow; acid stable; B122− and C2BeB2C2Pmmna=6.13425 b=5.4220 c=4.6928NaB5CPmma = 4.0925 Z=1density=2.16 black; air sensitiveNaB13C2Immaa = 10.9417 b = 5.6756 c = 8.0898 reddish black metallicMgB2C2Cmcaa = 10.922 b = 9.461 c = 7.459red transparent; brittle; layers ∞2 [BC]−MgB2C2Pnnma = 7.19633 b = 4.6179 c = 2.77714MgB12C2C2/ca=7.274 b=8.777 c=7.282 β=105.33° Z=4B12 and CMgB12C2Imma a=5.613 b=9.828 c=7.933 Z=4B12 and C2Mg1.42B25C4P21/cа = 9.626 b = 11.329 c = 8.966 β = 105.80° V = 940.8 Å3density=2.505 g/cm3MgB50C8Mg3B50C8C2/ma = 8.938 b = 5.6514 c = 9.602 β = 105.86° Z = 1(B12)4(CBC)2(C2)2 DicarbidoborateAlB40C4Al2B51C8diamond likeAl3BChexagonala=3.491 c=11.541Al3BC3Pc1a=5.900 c=15.900 V=479.0 Z=6light-yellow transparent; water stable; dissolve in HF or HNO3; CBC + AlC3 layers; density=2.66Al3B48C2diamond-likeMg3B36Si9CRma=10.079 c=16.372black; acid stable; Vickers hardness 17.0 GPaLiB12PCImmaa=10.188 b=5.7689 c=8.127 Z=4colourlessLiB12P0.89C1.11brownLiB12P1.13C0.87Immaa=10.410 b=5.9029 c=8.204redKB5CPmma=4.1281 Z=1black; air sensitiveCaB2C2I4/mcma = 5.3733 c = 7.4155 Z = 48 and 4 member rings of BC in sheets; CaB2C4P6/mmma = 4.55971 c = 4.4020CaB2C6P6/mmma = 2.58390 c = 4.43597Ca5Cl3(C2)(CBC)Cmcma=3.8924 b =13.891 c=18.59 V=1005.2orange-brown transparent; water sensitive; CC and CBCCa3Cl2CBNPnmacarbidonitridoborate CBN4−Ca15(CBN)6(C2)2F2Iada=16.5364dark red; decompose in moist air; carbidonitridoborate CBN4−Ca15(CBN)6(C2)2Ocarbidonitridoborate CBN4−Ca3(CBN)Br2carbidonitridoborate CBN4−Ca9Cl8(BC2)2Cmcma = 11.6291 b = 13.416 c = 12.0862 Z = 4pale red transparent; sensitive to dampness;ScB2CP42/mbca=6.651 c=6.763 V=299.1density 3.502; 2D net of seven and four-membered ringsScBC20-D BC2ScB2C2Pbama = 5.175 b = 10.075 c = 3.440tough, water resistant, melts over 2500 °CScB3C3Pmna = 4.609clathrate; metallic; air sensitiveScB17C0.25P6/mmma=14.550 c=8.4543Sc2BC2I4/mmma=3.3259 c=10.674 Z=2Sc2B1.1C3.2P3m1a=3.3991 c=6.7140 or a=23.710 c=6.703[B1/3C2/3]∞ with Sc-C-Sc layersSc3B5C3tetragonala=3.3308 c=7.680Sc3B0.75C3P4/mmma=3.33150 c=7.6737ScB15C0.80ScB15C1.60orthorhombica=10.027 b=8.0138 c=5.6668Sc12B185C9P6/mmma = 14.550 c = 8.954 V = 1641.7 Å3Sc20⁢BC27P4/ncca = 7.5042 c =10.0386superconductor Tc=7.8K; also ranging to Sc20B5C23ScB15.5CNP3m1a=5.568 c=10.756 Z=2ScB12.7C0.62Si0.08F43ma=20.3085ScB12.9C0.72Si0.004Pbama=17.3040 b=16.0738 c=14.4829ScB11.5C0.61Si0.04P62ma = 14.3055 c = 23.7477ScNi2B2CI4/mmma=3.34 c=10.2 V=114Fe23B3C3cubica=10.62Sr3Cl2[CBN]Pnmayellow; carbidonitridoborateYBCa = 3.38 b = 13.69 c = 3.62YB2CP42/mbca = 6.769 c = 7.430YB22C3Rma=5.623 c=44.765 V=1226.9YB28.5C Rma=5.649 c=56.899 V=1572.7YB2C2P4/mbma = 5.351 c = 3.561melt > 2500 °C; Young's modulus = 207 GPa, shear modulus = 87 GPa, bulk modulus = 116 GPa; degrades in water or moist air; Superconductor Tc=1.0 KYB22C2NRma=5.623 c=44.785Y2B3C2Cmmma=0.3405 b=1.3765, c=0.3631 Z=2 V=170.2Chain of B, with C branchesY5B2C5P4/ncca=8.1069 c=10.824 V=711.40D BC2 CY5B2C6P4a=8.068 c=11.668 v=7.595Y10.1B7C9.9C2/ca=11.27 b = 11.16 c = 23.57 β = 98.15° Z=8density 9.546; C-B-C and C-B-B-CY15B4C14(C4−)6(CBC5−)4•e−YB15.5CNPm1a=5.5919 c=10.873 Z=2Y2B36Si9CRma=10.0344Å c=16.348 Z=6YNi2B2CI4/mmma=3.525 c=10.536superconductor Tc 15.6KY2NiBC2Y5Ni6B6C5Y5Ni8B8C5Y16I19(C2B2C2)2Pa=12.311 b=13.996 c=19.695 α=74.96° β=89.51° γ=67.03°Y21I18(CBC)7Pa=10.660 b=15.546 c=18.41.6 α=82.49° β=85.01° γ=82.92°Nb3B3CCmcm a = 3.2647 b=28.710 c=3.1285 Z=4melt 2970 °CNb4B3C2Cmcma =3.2287 b= 37.544 c = 3.1331?Nb7B4C4Immma =3.15441 b=3.2166 c=32.260 Z=2?Nb7B6C3Cmmma = 3.1341 b = 33.161 c = 3.2428 Z=2?Mo2BCCmcma=3.086 b=17.35 c=3.047 Z=4superconductor Tc = 7.0 K; hard yet ductileYPd2B2Csuperconductor Tc = 23 KYPd5B3C0.3superconductor Tc=23KYRh2B2CBa21[BN2]11[C2]Ia = 15.3879 c = 10.0736 Z=2nitridoborate acetylideLaBCP212121 a = 8.646 b = 8.691 c = 12.479LaB2C2P4/mbma=3.816 c=3.975LaB2C42DLaB3C3Pmna =4.6712C6B6 forms truncated octahedron around La; semiconductorLa4B3C12La4B5C18La5B2C6P4a=8.5933 c=12.7098 V=938.56La5B4C4.85Pna21a=24.657 b=8.605 c=8.6540 Z=4 V=1836.2shiny blackLa10B9C6La10B9C12P41212a=8.6678 c=25.689 Z=4 V=1927.1shiny black plates; CCCBBCBCBBCCC CBCBBCBC 0D chainsLa15B14C19P21/ca=8.640 b=8.636 c=19.823 β=94.28La3BC2H1.69Cmcma=3.804 b=12.744 c=11.240La3BC2F~0.71Cmcma =3.8189 b=12.982 c=11.3585La3BC2Cl~0.71Cmcma =3.8409 b =13.7068 c=11.2820La3Cl2(CBC)Pnmaa=14.871 b=3.898 c=11.363La3Cl3BCP21/ma = 8.204 b = 3.8824 c = 11.328 β = 100.82◦ V=354.4 Z=2metallic; chain of B with C branchesLaNi2B2CI4/mmma=3.793 c=9.824La3Br2(CBC)Pnmaa=15.323 b=3.974 c=11.580La3Br3(BC)P21/ma=8.551 b=3.949 c=11.707 β=100.08La9Br5(CBC)3Pmmna=33.27 b=3.859 c=7.907superconductor Tc=6KLa4I5B2C C2/ma=23.303 b=4.299 c=18.991 β=126.22°La9I5(CBC)3 Pmmna=33.852 b=3.954 c=8.212CeBCP212121 CeB2CRma=6.6138 c=11.25942D 6 and 9 membered rings fusedCeB2C2P4/mbma=3.817 c=3.852Ce5B2C5P4/ncca=8.5708 c=11.004 v=808.3Ce5B2C6P4a=8.3654 c=12.5217 v=875.9Ce5B4C5Pna21a=24.426 b=8.463 c=8.5007 Z=8 V=1757blackCe10B8C100D B4C4 B3C3 BC2 CCe10B9C12P41212a = 8.4785 c = 18.223 V = 1822.3 Å3 Z = 4CCBCBCBCBCBCC9− CBCBBCBC8−Ce4B2C2H2.42C2/ma=12.895 b=3.7661 c=9.530 β=130.69°Ce4B2C2F0.14H2.26C2/ma=12.792 b=3.7475 c=9.478 β=130.65°Ce3BC2F~0.71Cmcma=3.7267 b=12.4893 c=11.1777Ce3Cl2(CBC)Pnmaa=14.690 3.836 c=11.260Ce3Cl3(BC) P21/ma=8.138 b=3.773 c=11.199Ce33Fe13B18C34Im-3ma = 14.246Ce10Co2.64B11.70C10Pa = 8.5131 b = 8.5144 c = 13.5709 α = 100.870° β = 93.677° γ = 90.041° Z = 2CeNi2B2CI4/mmma=3.6378 c=10.227Ce3Br2(CBC)Pnmaa=15.13.5 b=3.915 c=11.444Ce3Br3(BC)P21/ma=8.471 b=3.867 c=11.623 β=99.70°Ce9Br5(CBC)3Pmmna=32.935 b=3.804 c=7.816Ce6Br3(CB2C)CP2/ma=8.601 b=3.829 c=10.224 β=112.51°Ce4I5B2C C2/ma=23.194 b=4.290 c=18.822 β=126.50°CeRh2B2CI4/mmma=3.843 c=10.176CePd2B2CI4/mmmPrBCP212121 a = 8.4478 b = 8.4719 c = 12.325PrB2C2Pr2BCC2/m a = 13.088 b = 3.6748 c = 9.488 β = 131.03°Pr5B2C5P4/ncca=8.522 c=10.995 v=798.5