Surface and bulk crystallization in Nd2O3–Al2O3–SiO2–TiO2 glasses

A threshold heating rate for single‐stage heat treatments in glass‐ceramics containing seed formers

“…The addition of nucleating agents (also seed formers) has been exploited since the early stages of glassceramics development 4 to enhance and modulate glass crystallization. TiO 2 represents one of the bestestablished nucleating agents in aluminosilicate compositions [5][6][7][8][9][10][11] and its efficacy essentially relies on the strong temperature dependence of its melt solubility 12,13 : sufficiently fast melt quenching can indeed yield a glass that is metastably supersaturated in TiO 2 and therefore possesses a strong driving force for nucleation. TiO 2 -bearing nano-sized seeds, including TiO 2 (B), anatase and Mg-Al-titanate [14][15][16] , can subsequently homogeneously precipitate in the material upon reheating and catalyze the further heterogeneous nucleation of a functional phase, such as quartz solid solution (Qss) 17,18 in lithium and magnesium aluminosilicate glass-ceramics 10,11 .…”

Glass formation and devitrification behavior of alkali (Li, Na) aluminosilicate melts containing TiO2

“…Among such additives, TiO 2 represents one of the most versatile in aluminosilicate matrices: as a single seed former or in combination with ZrO 2 , it enables the production of a number of technologically relevant materials, including highstrength cordierite and spinel glass-ceramics and low-thermal expansion glass-ceramics based on quartz solid solutions (Qss) [2][3][4]. Despite being investigated since the early days of glass-ceramic development [5], however, the fundamental laws controlling the nucleation efficiency of TiO 2 in different compositional systems are still not fully understood: while 4 mol% are more than sufficient to induce volume crystallization in lithium aluminosilicate glass-ceramics (LAS) [6], higher additions (6-10 mol%) have been shown to be necessary in magnesium aluminosilicate (MAS) [7], sodium aluminosilicate (NAS) [8] and other multicomponent glasses [9][10][11][12][13]; conversely, TiO 2 was found to detrimentally foster surface nucleation in calcium aluminosilicate matrices [14]. The steady improvement of our analytical capabilities has recently shed new light on the complexity of seed formation, particularly within the LAS and MAS systems: (i) incipient liquid-liquid phase separation [15], (ii) a coupled increase in average coordination number of Ti and Al during crystal nucleation [16][17][18], (iii) the resulting pervasive nanostructural heterogeneity of the residual amorphous matrix [19,20] and (iv) the occurrence of TiO 2 (B) as a metastable precursor to the formation of anatase and rutile [21,22] represent only some of the crucial phenomena involved in TiO 2 nucleation which were disentangled in the past few years.…”

Effect of Rare Earth Oxide and Rare Earth-Alumina-Silica Glass on Mechanical Properties of Liquid Phase Sintered Alumina Ceramics

“…A large number of rare-earth-containing glasses have been developed for various applications involving laser, Faraday rotator and optical lenses with high refractive index [3]. The rare earth aluminosilicate glasses are attracting interest because of their high elastic modulus, hardness and high refractive index.…”