Vpliv nižjih vsebnosti itrijevega oksida na mehanske in optične lastnosti dentalne keramike iz cirkonijevega oksida : diplomsko delo

Lončar, Lea (author), Kocjan, Andraž (mentor), Markoli, Boštjan (comentor)

V diplomskem delu je bila raziskana primerjava mehanskih, mikrostrukturnih in optičnih lastnosti keramike iz cirkonijevega oksida (ZrO2), stabilizirane z različno vsebnostjo itrijevega oksida (Y2O3) (2 in 3 mol. %), z dodatkom aluminijevega oksida (Al2O3) ter sintrane po dveh različnih postopkih, konvencionalnem in hitrem. Namen raziskave je bil ugotoviti vpliv vsebnosti Y2O3, prisotnosti Al2O3 in izbranega postopka sintranja na trdnost, trdoto, lomno žilavost, velikost zrn, fazno sestavo ter prosojnost materiala, ki se uporablja v zobozdravstvu. Eksperimentalni del je zajemal pripravo vzorcev, merjenje gostote, določanje dvoosne upogibne trdnosti (ang. ball on three balls; krajše B3B-test), Weibullovo analizo, analizo lomnih površin s SEM (vrstični elektronski mikroskop, ang. Scanning Electron Microscope; krajše SEM), določitev trdote in lomne žilavosti po Vickersu, fazno analizo z rentgensko praškovno difrakcijo in optične meritve prosojnosti s pomočjo slikovne analize. Rezultati so pokazali, da so imeli vzorci z 2 mol. % Y2O3 višjo dvoosno upogibno trdnost in višje Weibullove module kot vzorci s 3 mol. % Y2O3, kar potrjuje vpliv transformacijskega utrjevanja. Dodatek Al2O3 je zaviral rast zrn in izboljšal homogenost mikrostrukture, kar se je odražalo v višji trdnosti in žilavosti. Hitro sintranje je v povprečju prineslo nekoliko višjo trdnost in lomno žilavost pri skupinah z 2 mol. % Y2O3, vendar nekoliko manjšo zanesljivost zaradi bolj heterogene mikrostrukture. Pri skupinah s 3 mol. % Y2O3 je bila opažena večja prosojnost vzorcev, s tem da je bila dosežena nižja lomna žilavost. Prav tako so vse napake v mikrostrukturi hitro sintranih vzorcev bolj izrazite in imajo večji vpliv na mehanske lastnosti kot pri konvencionalnem postopku, kjer se večji del tetragonalne faze transformira v monoklinsko. Keramika iz ZrO2 z 2 mol. % Y2O3 ter dodatkom Al2O3, pripravljena po postopku hitrega sintranja, se je izkazala kot material z zelo ugodno kombinacijo trdnosti in lomne žilavosti, medtem ko keramika iz ZrO2 s 3 mol. % Y2O3 ter dodatkom Al2O3 ostaja primerna za estetsko zahtevnejše restavracije zaradi večje prosojnosti.

• Language: Slovenian
• Keywords: cirkonijev oksid, itrijev oksid, transformacijsko utrjevanje, mehanske lastnosti, optične lastnosti, sintranje
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: L. Lončar
• Year: 2025
• Number of pages: XIV, 49 str.
• PID: 20.500.12556/RUL-173636
• UDC: 669
• COBISS.SI-ID: 257243395
• Publication date in RUL: 19.09.2025

Secondary language

• Language: English
• Title: The influence of lower yttria content on the mechanical and optical properties of dental zirconia ceramics : diploma work

Abstract

This thesis investigated the comparison of mechanical, microstructural and optical properties of ZrO2 ceramics stabilized with different contents of Y2O3 (2 and 3 mol. %), with addition of Al2O3, and sintered using two different protocols – conventional and rapid sintering. The aim of the research was to determine the influence of Y2O3 content, Al2O3 addition and sintering route on flexural strength, hardness, fracture toughness, grain size, phase composition and translucency of ZrO2 ceramics for dental applications. The experimental work included sample preparation, density measurement, biaxial flexural strength testing (B3B test), Weibull analysis, fracture surface analysis using SEM, hardness and fracture toughness measurement by the Vickers method, phase composition by X-ray diffraction and optical translucency measurement using image analysis. The results showed that samples with 2 mol. % Y2O3 exhibited higher biaxial flexural strength and higher Weibull moduli compared to those with 3 mol. % Y2O3, confirming the effect of transformation toughening. The addition of Al2O3 inhibited grain growth and improved microstructural homogeneity, which was reflected in higher strength and toughness. Rapid sintering generally resulted in slightly higher strength and fracture toughness in the samples with 2 mol. % Y2O3, but somewhat lower reliability due to a more heterogeneous microstructure. In the groups with 3 mol. % Y2O3, higher translucency was observed, accompanied by lower fracture toughness. Moreover, defects in the microstructure of rapidly sintered samples were more pronounced and had greater impact on mechanical properties than in the conventionally sintered samples, where a larger fraction of tetragonal phase transformed into monoclinic. ZrO2 ceramics with 2 mol. % Y2O3 and added Al2O3 prepared by rapid sintering, proved to be a material with very favourable combination of strength and fracture toughness, while ZrO2 ceramics with 3 mol. % Y2O3 and Al2O3 addition remain suitable for more aesthetically demanding restorations due to their higher translucency.

• Keywords: Zirconium Dioxide, Yttrium Oxide, transformation toughening, mechanical properties, optical properties, sintering