Abstract: (22 Views)
ZrO2 is commonly incorporated into ceramic glass substrates to enhance radiopacity, mechanical strength, and chemical durability. Experience has shown that the crystallization of tetragonal zirconia in glass will have a greater effect on the mechanical properties of ceramic glass. To achieve optimal properties in zirconia, stabilizing oxides are often added to enhance its structural and mechanical qualities. In this research, in order to stabilize the tetragonal phase of zirconia, MgO and CeO2 were added to the glass ceramic composition of the Li2O-SiO2-ZrO2 system and the desired dental substrate was synthesized through the sinter process. The behavior of sintering and crystallization of basic and optimized glass was investigated using HSM and DTA thermal analysis, respectively. The results showed that the optimal sinter temperature, heat press and heat treatment are equal to 730°C, 900°C and 825°C, respectively. Then, in order to determine the crystallization behavior of the prepared samples, X-ray diffraction and microstructure images were used. The results also showed that the presence of the main Li2ZrSi6O15 phase crystallizes at a temperature of 825°C in the base sample and the sample containing ceria. Also, due to early formation of MgSiO3 crystals, magnesia prevents sintering and formation of Li2ZrSi6O15 phase and stability of tetragonal zirconia phase. In the sample containing ceria, during crystallization, ZrO2 entered its crystal structure and led to the stability of the tetragonal zirconia phase at room temperature.
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According to the XRD and SEM test results, re-heat treatment causes phase
dissolution in the base sample and lack of formation of Li2ZrSi6O15 main phase.
According to the HSM chart, the shrinkage at 825°C is due to the formation of
Li2ZrSi6O15 phase, for this reason, this temperature is the optimal heat treatment
temperature. The presence of ceria in the sample heat treated at 825°C caused the
stability of the tetragonal zirconia phase in this sample because no peak containing
monoclinic zirconia was seen in this sample, and also in the XRD pattern, the shift
of the tetragonal zirconia peak to the left compared to the base sample and also We
can see the decrease in the intensity of the peak, which is caused by the presence of
ceria in the structure of zirconia, in the base sample and the sample containing
magnesia, we see the presence of monoclinic zirconia, which indicates the lack of
stability of the zirconia phase in these two samples, as well as early crystallization.
MgSiO3 prevents sintering of this sample