{"id":9114,"date":"2019-11-14T07:17:47","date_gmt":"2019-11-14T07:17:47","guid":{"rendered":"https:\/\/www.upjs.sk\/informacie\/vyskum\/vedeckovyskumna-cinnost\/spickove-timy\/qmagna-tim\/aktuality\/22029-2\/"},"modified":"2023-06-30T10:45:24","modified_gmt":"2023-06-30T09:45:24","slug":"22029-2","status":"publish","type":"post","link":"https:\/\/www.upjs.sk\/22029-2\/","title":{"rendered":"Konverzn\u00fd polymorfizmus: pr\u00edprava nov\u00fdch typov materi\u00e1lov"},"content":{"rendered":"\n
Mnoho tuh\u00fdch f\u00e1z, ktor\u00e9 s\u00fa v rovnov\u00e1he pri vysokom tlaku a vysokej teplote, je mo\u017en\u00e9 r\u00fdchlo ochladi\u0165 na okolit\u00e9 podmienky, kde zost\u00e1vaj\u00fa kineticky stabiln\u00e9 (zvy\u010dajne ozna\u010dovan\u00e9 ako metastabiln\u00e9 f\u00e1zy). Tieto f\u00e1zy ve\u013emi \u010dasto predstavuj\u00fa nov\u00e9 \u0161truktur\u00e1lne polymorfy s u\u017eito\u010dn\u00fdmi a jedine\u010dn\u00fdmi vlastnos\u0165ami.<\/p>\n\n\n\n
V predkladanej pr\u00e1ci sme systematicky \u0161tudovali transform\u00e1ciu perovskitov\u00fdch f\u00e1z a ich magnetick\u00e9 vlastnosti v celej s\u00e9rii BiFe1-y<\/sub>Scy<\/sub>O3<\/sub>. V pr\u00edpade kompoz\u00edci\u00ed s y<\/em> \u2265 0,2 sa perovskitov\u00e9 f\u00e1zy m\u00f4\u017eu stabilizova\u0165 iba za podmienok vysok\u00e9ho tlaku a metastabiln\u00e9 f\u00e1zy sa podrobili tepelnej \u00faprave po synt\u00e9ze. V\u00fdsledkom bolo pozorovanie sady ireverzibiln\u00fdch f\u00e1zov\u00fdch transform\u00e1ci\u00ed stimulovan\u00fdch \u017e\u00edhan\u00edm medzi r\u00f4znymi metastabiln\u00fdmi perovskitov\u00fdmi f\u00e1zami. Toto pozoruhodn\u00e9 spr\u00e1vanie n\u00e1m umo\u017enilo z\u00edska\u0165 tieto perovskity v r\u00f4znych stabiln\u00fdch polymorfoch, ktor\u00e9 predstavuj\u00fa nov\u00e9 \u0161trukt\u00fary so zauj\u00edmav\u00fdmi magnetick\u00fdmi vlastnos\u0165ami. Obzvl\u00e1\u0161\u0165 bola z\u00edskan\u00e1 nov\u00e1 ortorombick\u00e1 modifik\u00e1cia BiScO3<\/sub> s f\u00e1zov\u00fdm prechodom z neobvykl\u00e9ho koline\u00e1rneho magnetick\u00e9ho z\u00e1kladn\u00e9ho stavu na cykloidn\u00fa \u0161trukt\u00faru v pol\u00e1rnej modifik\u00e1cii R3c<\/em> syst\u00e9mu so zlo\u017een\u00edm BiFe0.7<\/sub>Sc0.3<\/sub>O3<\/sub>.<\/p>\n\n\n\n Hovor\u00edme o ireverzibiln\u00fdch transform\u00e1ci\u00e1ch ako o \u201ekonverznom polymorfizme\u201c a dokazujeme, \u017ee ide o pomerne v\u0161eobecn\u00fd jav, ktor\u00fd sa pravdepodobne prehliadol v mnoh\u00fdch \u010fal\u0161\u00edch metastabiln\u00fdch f\u00e1zach. V\u00fdsledky n\u00e1\u0161ho \u0161t\u00fadia boli publikovan\u00e9 v prest\u00ed\u017enom \u010dasopise Chemical Communications [D.D. Khalyavin et al., Chem. Commn. 55 (2019) 4683-4686<\/em>] s impaktov\u00fdm faktorom 6,164<\/strong>, ktor\u00fd je zahrnut\u00fd v indexe Nature.
DOI: http:\/\/dx.doi.org\/10.1039\/C9CC00472F<\/p>\n\n\n\n