Secondary crystal phase

In glass-ceramic El, a useful secondary crystal phase of P-spodumene reduced the linear thermal expansion coefficient to approximately 68 X 10-7 K-i... 

The nucleation and crystallization of the bulk glasses were induced in heat treatments, generally conducted in a two-step procedure in the range of 800°-1000°C. Pavluskin (1986) showed that the process involved is one of controlled crystallization in a phase-separated glass. In his report, he wrote that wollastonite and anorthite developed as the main crystal phases. The secondary crystal phases developed as diopside, pyroxene, or gehlenite. Depending on the composition, however, the secondary crystal phases may represent the main crystal phases and vice versa. 

The desired main crystal phase of the phlogopite type was formed at temperatures above 850°C, entirely consuming the norbergite. Fluorborite, Mg3(B03)F3 developed as a secondary crystal phase. Optimal microstructure formation, however, occurred at 950 C. 

P-Ca(P03)2 always formed the main crystal phase and small amounts of 2CaO 3P205 the secondary crystal phase. 

For the calculation of the phase diagrams using coupled analysis of thermodynamic and phase diagram data, the thermodynamic data represent enthalpies of fusion, enthalpies of mixing, heat capacities, and all other data that are available from the literature. The phase diagram data are the measured temperatures of primary crystallization, temperatures of secondary crystallization, etc. as well as the temperatures of the eutectic temperatures. 

In the Range IV, only the T2 for the amorphous phase decreases with time gradually. Other parameters are almost constant. Namely, only in the amorphous phase, the slight change of the structure takes place. This range seems to correspond to the so-called secondary crystallization. Thus, it is possible to investigate the crystallization dynamics by pulse NMR. 

The melting behavior of miscible crystallizable blends (section 3.3.5) is often complex, revealing multiple DSC endotherms, which can be ascribed to several causes such as recrystallization, secondary crystallization, liquid-liquid phase separation (3.3.6), etc. 

The melting behavior of binary crystallizable blends often reveals multiple melting endotherms, that can be ascribed to recrystallization, secondary crystallization effects, phase separation, etc. 

It can be seen that the isothermal conversion process became increasingly slower when the form II of PB-1 was crystallized from the melt in the presence of increasing amounts of HOCP. This trend was observed at all aging temperatures except 69°C. It was also noted in the slow phase transformation curves that complete conversion of residual small amount of form II into form I was exceedingly slow. This might have been due to continuous supplies of form II from the amorphous phase by secondary crystallization of the PB-1 (51). 

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