P<SUB>2</SUB>O<SUB>5</SUB> AS AN EFFECTIVE NUCLEATING AGENT OF LITHIUM DISILICATE GLASS-CERAMICS

Abstract

The objective of the study was to control the nucleation and main crystal formation of lithium disilicate, Li2Si2O5 , by an effective nucleating agent to develop high-strength,translucent glass-ceramics .The authors used P2O5 as nucleating agent to precipitate lithium disilicate in glasses derived from the SiO 2-Li 2O-Al2O3-K2O-ZrO2 system. The concentration of P2O5 was up to approx . 3 wt.%. Additives of P2O5 allowed the control of bulk crystallization . Nucleation was catalyzed by Li3PO4 phases . Li3PO4 is the heterogeneous catalyst . The final glass-ceramic is characterized by a dense microstructure with a high crystalline content of more than 70 vol .%.The mechanical strength was determined as biaxial flexural strength of approx . 740 MPa and Weibull factor of 11 .3. The glass-ceramic shows the potential to be applied as a biomaterial for dental restorations. The authors conclude the effectiveness of P2O 5 as nucleating agent on the basis of a heterogeneous nucleation of nanophases and precipitating main crystal phases by epitaxial growth .

Properties and Crystallization Phenomena in Li2Si2O5–Ca5(PO4)3F and Li2Si2O5–Sr5(PO4)3F Glass–Ceramics Via Twofold Internal Crystallization

“…Nevertheless, the microstructural effects of Li 2 Si 2 O 5 crystals dominate the mechanical properties. The influence of their size and morphology on the strength of glass–ceramics have been established by various authors in a multitude of investigations (Cramer von Clausbruch et al, 2000; Höland et al, 2005; Apel et al, 2007, 2008; Zheng et al, 2008; Dittmer et al, 2014). In summary, a high volume fraction of interlocking lath-like Li 2 Si 2 O 5 crystals yields high-strength materials.…”

“…In summary, a high volume fraction of interlocking lath-like Li 2 Si 2 O 5 crystals yields high-strength materials. The most efficient way of controlling the microstructure of lithium disilicate glass–ceramics derived from bulk glasses is by means of internal nucleation sites, in most cases via the content of P 2 O 5 (Cramer von Clausbruch et al, 2000; Höland et al, 2005). Similar to the results of numerous studies presented so far in the systems SiO 2 –Li 2 O–Al 2 O 3 –K 2 O–(ZrO 2 )–P 2 O 5 (Höland et al, 2006; Höland and Beall, 2012), the findings of the present work clearly suggest the nucleating effect of the P 2 O 5 content on the microstructure (Figure 4) and the biaxial strength as demonstrated in Figure 8.…”

“…Amorphous or disordered nanoscale Li 3 PO 4 phase separations play an uncontroversial role in the nucleation mechanism of lithium silicate. Based on the sound knowledge about nucleation and crystallization mechanisms, materials for restorative dentistry with a toughness of up to 2.9 MPa*m 0.5 and flexural biaxial strength up to 600 MPa with well-suited optical properties could be achieved (Cramer von Clausbruch et al, 2000; Höland et al, 2005; Apel et al, 2007, 2008; Höland and Beall, 2012). Furthermore, Li 2 Si 2 O 5 glass–ceramics are suited for various processing techniques, such as sintering, molding, and CAD/CAM machining in an intermediate Li 2 SiO 3 stage of the glass–ceramic.…”

Controlled Parallel Crystallization of Lithium Disilicate and Diopside Using a Combination of Internal and Surface Nucleation

“…Technical glass-ceramics as well as consumer applications were developed this way (Beall, 1992(Beall, , 2014Echeverría, 1992). Likewise, Höland et al (1994Höland et al ( , 2005Höland et al ( , 2007Höland et al ( , 2008Höland et al ( , 2009) succeeded in the development of lithium disilicate glass-ceramics for dental applications using such multicomponent base glass systems.…”

Examining the phase evolution of lithium disilicate glass‐ceramics with lithium tantalate as a secondary phase

“…These compositions also consist of other components like Al 2 O 3 for chemical durability and a nucleating agent to aid in the control of nucleation. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Past work studying lithium disilicate glass-ceramics has revealed much about the evolution of lithium metasilicate (Li 2 SiO 3 ) into lithium disilicate as the primary phase of these materials. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Lithium metasilicate is the primary phase at lower growth temperatures because it has a higher growth rate initially.…”