Úvod
Vysokoteplotní supravodiče obvykle odkazují na materiály, které jsou supravodivé nad teplotou kapalného dusíku (77 K). Uplynulo pět let od té doby, všechny supravodiče, které byly objeveny, vykazují supravodivost pouze při extrémně nízkých teplotách (23 K), takže jejich aplikace byla značně omezena.
Discovery
In1986,BernozandMullerdiscoveredthe35Ksuperconductinglanthanumbariumcopperoxygensystem.Thisbreakthroughdiscoveryledtothediscoveryofaseriesofrareearthbariumcopperoxidesuperconductorsathighertemperatures.Throughelementreplacement,atthebeginningof1987,WuMaokun(ZhuJingwu)oftheUnitedStatesandZhaoZhongxianoftheChineseInstituteofPhysicsannouncedthediscoveryofa90Kyttrium-barium-copper-oxygensuperconductor,achievingthefirstbreakthroughinthetemperaturebarrierofliquidnitrogentemperature(77K).BernozandMulleralsowonthe1987NobelPrizeinPhysicsfortheirpioneeringwork.
Thistypeofsuperconductorisusuallycalledahigh-temperaturesuperconductorbecauseitscriticaltemperatureisabovethetemperatureofliquidnitrogen(77K).Thediscoveryofyttrium-barium-copper-oxygensuperconductorsabovethetemperatureofliquidnitrogenhasprovidedordinaryphysicslaboratorieswiththeconditionsforconductingsuperconductingexperiments.Therefore,therehasbeenanupsurgeinexploringnewhigh-temperaturesuperconductorsaroundtheworld.Attheendof1987,ChinesescholarShengZhengzhiandothersfirstdiscoveredthefirstrareearth-freethallium-barium-copper-oxygenhigh-temperaturesuperconductor.Inearly1988,Japandevelopedabismuth-strontium-calcium-copper-oxygensuperconductorwithacriticaltemperatureof110K.InFebruary1988,ShengZhengzhiandothersfurtherdiscoveredthe125Kthalliumbariumcalciumcopperoxygensuperconductor.Afewyearslater(1993)Frenchscientistsdiscovereda135Kmercury-barium-calcium-copper-oxygensuperconductor.
Classification
High-temperaturesuperconductorsincludefourcategories:90Krareearthseries,110Kbismuthseries,125Kthalliumseries,and135Kmercuryseries.Theyallcontaincopperandoxygen,sotheyarecollectivelyreferredtoascopper-basedsuperconductors.Theyhaveasimilarlayeredcrystallinestructure,andthecopperoxidelayerisasuperconductinglayer.High-temperaturesuperconductorshavealreadyachievedpracticalapplicationsandhavebeguntobenefitmankind.Forexample,yttrium-barium-copper-oxygensuperconductorsandbismuthsuperconductorshavebeenmadeintohigh-qualitysuperconductingcables.Thedevicemadeofthallium,barium,calcium,copperandoxygensuperconductingfilmwasinstalledinthetransmissiontowerofmobilephonesasearlyastheendofthelastcenturytoincreasecapacityandreducedisconnectionandinterference.
Příklady
Vysokoteplotní supravodivé supravodiče oxidů mědi zahrnujía1,85Ba0,15CuO4 a YBCO (sloučenina yttrium-barium-měď-kyslík), což jsou oba známé materiály pro proražení kapalného dusíku"(Teplota 7KB).
203 | H2S(150GPvysoký tlak) | Supravodič na bázi vodíku |
195 | Bod sublimace suchého ledu | |
138 | Hg12Tl3Ba30Ca30Cu45O127 | Supravodič oxidu mědi |
110 | Bi2Sr2Ca2Cu3O10(BSCCO) | |
92 | YBa2Cu3O7(YBCO) | |
77 | Bod varu kapalného dusíku | |
43 | SmFeAs(O,F) | Supravodič na bázi železa |
41 | CeFeAs(O,F) | |
26 | LaFeAs(O,F) | |
20 | Bod varu kapalného vodíku | |
18 | Nb3Sn | Metal-teplotní supravodič |
10 | NbTi | |
4.2 | Hg (rtuť) |
Výhled
Průzkum nových a vyšších teplotních supravodičů probíhá intenzivně. čas od času nebyly učiněny skutečné nové průlomy.
Whydomanysuperconductingmaterialsneedtobesuperconductingataverylowtemperature?Itisbecauseatroomtemperature,therearegapsbetweenconductoratoms.Whenelectronsmovebetweenatoms,theymustpassthroughthesegapsandcollidewiththeatoms,causingtheatomstovibrateandheattoformresistance.Atextremelylowtemperatures,therearealmostnogapsbetweenconductoratoms,andelectronscanpassfreelywithoutcollidingwithatoms.Inthefuture,theresearchofroomtemperaturesuperconductingmaterialsshouldselectappropriatemixturesofdifferentelements,sothatatomsofdifferentsizesandshapesarecombinedtogether,sothattherearenogapsbetweenatoms,sothatelectronscanpassthroughfreelyanddonotcollidewithatoms.Thedifficultyinthedevelopmentofroomtemperaturesuperconductingmaterialsisthattheatomsofmanymaterialswillvibrateatroomtemperature,andthegapsbetweentheatomsarerelativelylarge.Aslongasthemixingelementsareproperlyselected,superconductingmaterialsatroomtemperaturecansoonbemass-produced.
WebelievethatthedescendantsofYanhuang,whohavemadeoutstandingachievementsinthefieldofcopper-basedhigh-temperaturesuperconductors,willcertainlymakemorebrilliantcontributionstothejourneyofrealizingthedreamofhumanroomtemperaturesuperconductors.
kritická přechodová teplotaTc( Kelvin, K) | Materiál/bod varu látky | Typ |
138 kB | Hg12Tl3Ba30Ca30Cu45O127 | Supravodič oxidů mědi |
110 kB | Bi2Sr2Ca2Cu3O10(BSCCO) | |
92 kB | YBa2Cu3O7(YBCO) | |
77 kB | N2 | —— |
43 kB | SmFeAs(O,F) | Supravodič na bázi železa |
41 kB | CeFeAs(O,F) | |
26 kB | LaFeAs(O,F) | |
20 tis | H2bod varu | —— |
18 kB | Nb3Sn | Metal-teplotní supravodič |
10 tis | NbTi | |
4,25 kB | Je bod varu | —— |
4,2 kB | Hg (rtuť) | Kovový supravodič |