Of P-quartz solid solution

Figure 1-7 Unit cell dimensions and Cg of p-quartz solid solutions between SiOg and p-eucryptite (UAISiO ) (empty squares). Full squares correspond to peraluminous p-quartz solid solutions between LiAl 78164 25 and SiOg (after Nakagawa and Izumitani, 1972).

Similarly, the refractive index and birefringence of P-quartz solid solutions can be varied over a considerable range. Figure 1-10 shows the indices of refraction of quartz solid solutions along the Si02-MgAl20 join (Schreyer and Schairer, 1961). It can... 

The basic process development for the production of P-quartz solid solution glass-ceramics was conducted by Corning Glass Works. The key to the controlled crystallization of P-quartz solid solution was soon shown to be controlled nucleation, in other words, the correct selection of the nucleating agents and their concentration. 

Beall et al. (1967) developed an effective nucleation initiation method for the precipitation of very small crystals of the P-quartz solid solution type in the Si02-Al203-Li20-Mg0-Zn0 system. Nucleation for the subsequent crystallization of P-quartz solid solution was achieved with additions of Ti02, Zr02, and occasionally Ta205 (Beall et al., 1967 Beall 1992). The desired crystallites of less than 100 nm were achieved in the crystallization of P-quartz solid solution which followed nucleation. Therefore, the fabrication... 

Titanium ions are enriched in the droplet phase containing Al and cause heterogeneous crystallization of P-quartz solid solution. 

The compositions of P-quartz solid solution glass-ceramics produced on a large scale for technical applications are summarized in Table 2-7. These glass-ceramics are called Vision , Zerodur , Narumi , Neoceram , Ceran , and Keraglas . Other products are Robax , which represents a col-... 

Glass-ceramics in which gahnite, Zn0 Al203, and P-quartz solid solution constitute the main crystal phase were introduced by Strnad (1986). The typical range of the chemical composition of P-quartz solid solution-gahnite glass-ceramics is shown below ... 

The formation of P-quartz solid solution and gahnite crystals in glass-ceramics from the Si02-Al203—ZnO allowed specific properties, such as translucency and even transparency, to be combined with variable coefficients of thermal expansion of... 

This type of cellular membrane microstructure can be developed in glass-ceramics that exhibit a very low coefficient of thermal expansion because of the precipitation of p-quartz solid-solution or P-spodumene crystals (Beall 1992). The glass matrix, which is very thin and surrounds the crystals, plays the part of the cellular membrane. As a result, the crystals are separated from each other. The membrane accounts for approximately 10 vol% of the micro-structure and can, for example, act as a diffusion barrier between the crystals. 

Figure 3-2 shows the cellular membrane microstructure of a P-quartz solid solution glass-ceramic. The individual phases are presented in connection with their effect on the different solid-state reactions to provide a better understanding of this microstructure. As described in Section 2.2.2, the nucleation of P-quartz solid-solution crystals is heterogeneously initiated by ZrTiO nucleating agents. These ZrHO crystals represent the nucleus of the... 

Beall (1992) attributes a great deal of importance to the glass matrix representing the cellular membrane in the solid-state reactions of P-quartz solid solution and P-spodumene solid solution glass-ceramics, the tenacious residual... 

In the development of glass-ceramics of the P-quartz solid solution type, all three requirements were met similarity of the index of refraction between the glass matrix and the crystals, very small particle size, and low absorption. The solid-state reactions that are involved in the formation of P-quartz solid solution glass-ceramic are presented in Section 2.2.2. The chemical composition of different products are also discussed in this section. The special nanostructure of this glass-ceramic is described in Section 3.2.1. 

The main crystal phase of the Zerodur glass-ceramic is composed of P-quartz solid solution This phase is produced by volume crystallization. Special thermal properties devdop as a result of the formation of very small crystallites and the simultaneous high crystallite count per unit of glass volume. 

---