20.500.12556/DKUM-41285 SINTRANJE IN STEREOLOŠKA ANALIZA MIKROSTRUKTURE ELEKTROKALORIČNE KERAMIKE NA OSNOVI Pb(Mg1/3Nb2/3)O3 -PbTiO3 SINTERING AND STEREOLOGICAL ANALYSIS OF ELECTROCALORIC CERAMICS BASED ON Pb(Mg1/3Nb2/3)O3 -PbTiO3 V diplomskem delu smo po različnih časih sintranja pri 1200 °C pripravili keramiko na osnovi 0,65Pb(Mg1/3Nb2/3)O3–0,35PbTiO3, ki izkazuje dobre elektrokalorične lastnosti. Opravili smo stereološko analizo mikrostrukture in izmerili dielektrične, feroelektrične in piezoelektrične lastnosti. Namen dela je bil pripraviti vzorce z različno velikostjo zrn in porazdelitvijo velikosti zrn in izmeriti snovne funkcijske lastnosti. Iz mešanice kovinskih oksidov v ustreznem stehiometrijskim razmerju smo z mehanokemijsko aktivacijo v visokoenergijskem planetarnem mlinu pripravili keramični prah. Z rentgensko fazno analizo smo pokazali, da prah sestavlja le perovskitna faza. Srednja velikost delcev prahu je bila 0,325 µm. Z meritvijo skrčka stisnjene tablete, v odvisnosti od temperature, smo v segrevalnem mikroskopu določili temperaturno območje sintranja. Z različno dolgimi časi sintranja pri 1200 °C, od 0,1 ure do 16 ur, smo pripravili štiri vzorce. Rentgenska fazna analiza je pokazala, da je v sintranih vzorcih prisotna perovskitna faza, vendar smo v spektrih vzorcev zasledili prisotnost sledov piroklorne faze, katere delež se z daljšanjem časa sintranja povečuje. Relativna gostota se je s časom sintranja zmanjševala, od 98,1 % za vzorec sintran 0,1 uro, do 93,3 % za vzorec sintran 16 ur. S stereološko analizo mikrostrukture smo ugotovili, da se velikost zrn z daljšanjem časa povečuje. S preprosto linearno enačbo smo zapisali funkcijo velikosti zrn po času sintranja v časovnem intervalu od 0,1 do 16 ur. Mikrostruktura in gostota keramike vplivata na relativno dielektričnost pred polarizacijo 4300 in po polarizaciji 5670, remanentno polarizacijo 30,1 µC/cm2, koercitivno polje 5,7 kV/cm in piezoelektrični koeficient d33 600 pC/N. Slednje vrednosti je izkazala keramika, sintrana 8 ur, z relativno gostoto 96,2 % in srednjo velikostjo zrn 3,20 ± 1,63 µm. The aim of the diploma thesis was to prepare the 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 based ceramics with different grain sizes and to analyse the microstructure of the samples, sintered at different times. The characterization of dielectric, ferroelectric and piezoelectric properties of the material was also performed. The 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 powder was prepared by mechanochemical activation of the mixture of individual oxides in the stoichiometric ratio. The X-ray powder diffraction analysis revealed that the as-synthesized powder crystallized in the perovskite phase. The median particle size was 0.325 µm. The sintering curve of the powder compact was determined by a heating-stage microscope. Four ceramic samples were prepared by sintering the powder compacts at 1200 °C at times from 0.1 to 16 hours. According to the X-ray powder diffraction analysis the samples consisted of the perovskite phase, however a low amount of the non-ferroelectric pyrochlore phase was also detected in the diffractograms, and its amount increased with sintering time. The relative density of the samples decreased with the sintering time from 98.1 % to 93.3 % for the samples sintered for 0.1 and 16 hours, respectively. The stereological analysis revealed that the mean grain size and also the width of the grain size distribution increased with increasing sintering time. A linear relationship of the mean grain size versus the sintering time was observed within the measured time interval. We observed that the density and microstructure of the ceramics influenced the dielectric, ferroelectric and piezoelectric properties. The relative dielectric permittivity, remanent polarization, coercive field and piezoelectric coefficient d33 of the ceramic, sintered for 8 hours, with the 96.2 % relative density and the mean size of 3.20 ± 1.63 µm were 4300 (virgin) and 5670 (after poling), 30.1 µC/cm2, 5.7 kV/cm and 600 pC/N, respectively. PMN PT mehanokemijska sinteza sintranje mikrostruktura stereološka analiza dielektričnost PMN PT mechanochemical synthesis sintering microstructure stereological analysis dielectricity true true false [A. Matavž] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2013-08-20 09:31:31 2013-09-06 12:09:58 2022-05-04 03:07:03 2021-04-25 03:14:37 2013 0 Maribor 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 546.47.057(043.2) 17488150 URN:SI:UM:DK:R7PT6PO6 UNI_Matavz_Aleksander_2013.pdf UNI_Matavz_Aleksander_2013.pdf 1 8F286ACD760F92723D2B1BF514E0AF8A 60227ac724b54a1748d5adcafe6460558b3b84d56547ae610495e32170028de4 23ec7f5f-7c0a-11eb-bb7a-00155d0001ca https://dk.um.si/Dokument.php?lang=slv&id=57006 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0