In　2002,　researchers　at　the　Tokyo　Institute　of　Technology　synthesized　a　new　inorganic　mayenite　electride-12CaO•7Al2O3:2e-　(hereinafter　C12A7:e-),　as　a　potential　transparent　conductive　oxide,　which　opened　a　new　chapter　in　electride　synthesis　and　utilization.　Compared　with　other　organic　electrides,　it　has　better　chemical　stability　and　can　be　stable　in　air　below　450.This　thermally　stable　electride　has　a　number　of　potentially　useful　properties,　such　as　air-stability,　low　work　function,　excellent　performance　in　resisting　poisoning,　and　metallic　conductivity.　Thermal　stability　and　low　reactivity　with　air　make　this　material　has　a　broad　application　prospect　in　electron　emitter,　optical　device,　catalyst　support　and　other　fields.　Especially,　C12A7:e-　has　been　found　to　have　certain　emission　performance　at　low　temperature　and　is　very　suitable　as　a　electron　emission　material　for　low-power　vacuum　electronic　devices.　Compared　with　commercialized　cathode　materials,　such　as　Ni(5.0　eV),　Mo(4.6　eV)　and　LaB6(2.67　eV),　C12A7:e-exhibits　low　work　function　(~2.4　eV).　On　the　other　hand,　the　strong　chemical　bond　force　in　C12A7　crystal　makes　it　have　better　ion　bombardment　resistance.　The　sputtering　effect　of　ion　bombardment　on　the　cathode　at　work　has　an　impact　influence　on　the　service　life.　Furthermore,　the　search　for　other　inorganic　electrides　is　a　very　promising　area　of　study.　Due　to　the　prolonged　synthesis　cycle　and　special　encapsulation,　in　the　past　decade,　substantial　efforts　have　been　devoted　to　seeking　simple　and　efficient　route　to　acquire　the　electride　in　desire　forms.　So　far,　various　forms　of　mayenite　electride　have　been　realized,　mainly　including　single　crystal,　thin　film　and　polycrystalline.　These　researchers　have　been　working　to　make　full　use　of　the　advantages　of　C12A7:e-　applications　while　significantly　reducing　the　preparation　cycle　and　increasing　the　electron　concentration.　Now,　the　electron　concentration　of　C12A7:e-　can　reach　2.3×1021　cm-3,　which　is　close　to　the　theoretical　electron　concentration　of　2.33×1021　cm-3.The　conductivity　at　room　temperature　also　jumped　from　0.3　S•cm-1　in　2002　to　1　380　S•cm-1.　Since　Hayashi　found　that　C12A7:H-　can　be　changed　from　an　insulator　to　an　electrical　conductor　C12A7:e-　after　being　exposed　to　ultraviolet　light,　many　scholars　have　been　working　on　developing　more　efficient　and　rapid　preparation　methods.　In　2003,　Matsuishi　et　al.　prepared　C12A7:e-　with　high　electron　concentration　(2×1021　cm-3)　by　Ca　metal　vapor　reduction,　but　this　method　would　form　a　dense　CaO　film　on　the　sample　surface　and　hinder　the　continuation　of　reduction,　resulting　in　too　long　reduction　time.　After　that,　Hosono　effectively　reduced　reduction　time　by　replacing　Ca　metal　with　Ti,　but　metal　vapor　reduction　could　not　reduce　C12A7:e-　film.　In　2006,　the　CO/CO2　atmospheric　reduction　solved　this　problem,　but　the　sample　prepared　had　a　low　electron　concentration　(Ne~1.4×1019　cm-3).Recently　developed　by　our　team　of　SPS　combinate　with　Ti　metal　vapor　reduction　method　and　in-situ　aluminothermic　reduction　process,　can　manufacture　the　high　electron　concentration　(Ne~2.3×1021　cm-3)　C12A7:e-　block　within　0.5　h.　These　two　methods　need　the　shortest　reduction　time,　lowest　cost,　and　are　the　easiest　way　to　mass　production　in　many　preparation　methods,　they　overcome　many　problem,　such　as　the　long　preparation　period,　large　energy　consumption　and　low　electron　concentration,　which　laid　a　foundation　for　its　large-scale　application.　However,　those　methods　still　has　great　limitations,　because　they　can　only　be　used　to　prepare　C12A7:e-　polycrystalline　block.　This　paper　summarizes　the　preparation　methods　of　C12A7:e-　single　crystal,　thin　film　and　polycrystalline,　compares　the　advantages　and　disadvantages　of　each　preparation　method,　analyzes　the　problems　faced　by　the　preparation　of　the　material　and　prospects　its　application,　in　order　to　provide　reference　for　finding　a　more　rapid　and　effective　preparation　method.　©　2020,　Materials　Review　Magazine.　All　right　reserved.