Synthesis and Thermal Expansion of β‐Eucryptite Powders Produced by the Inorganic–Organic Steric Entrapment Method

Abstract

The characterization of powders prepared using the inorganic–organic steric entrapment method was explored and compared to the conventional solid‐state route, using X‐ray diffraction, differential scanning calorimetry, particle size analysis, and specific surface area measurements. β‐eucryptite was crystallized at 627°C and the properties of the resulting powder allowed for increased densification upon sintering compared to conventional methods. The thermal expansion behavior was also determined in situ using X‐ray diffraction and was found to be similar to other published studies, but thermal expansion in all {hkl} pole directions has been measured.

Comparative study of titanate syntheses by the organic steric entrapment method

“…This serves to decrease the mobility of metal ions and constrain the system to prevent precipitation of cationic species and agglomeration. The organic–inorganic powder synthesis method involves mechanical, steric entrapment, but also some chemical chelation, as is schematically depicted in Figure 1 for an example of CaAl 2 O 4 synthesized by the PVA method 2–36 . At the optimum amount of polymer, the metal ions are dispersed in solution and a homogeneous, polymeric network is formed which prevents them from precipitating.…”

“…However, by using in situ EG polymerization around the Ti 4+ species, this process can be extended to chemicals that decompose in water and precipitate out of solution, such as titanium isopropoxide Ti[(OCH(CH 3 ) 2 ] 4 or “TISO.” 3 In the case of titanate powder, EG can act as an effective solvent for wet chemical synthesis, because a water‐soluble titanium salt is not available commercially. The polymerizing agent, EG in this method, acts to capture the metal ions by polymerizing around the dissolved Ti 4+ species resulting in a steric entrapment mechanism as in the PVA method 2–35 . This serves to decrease the mobility of metal ions and constrain the system to prevent precipitation of cationic species and agglomeration.…”

“…However, the process is often expensive and complicated. The organic steric entrapment method using polyvinyl alcohol (PVA), polyethylene glycol (PEG), or ethylene glycol (EG) as a polymer carrier has been developed to facilitate and make the soft solution processing more efficient 2–35 . The PVA, partially substituted with 17 mol% acetate groups, ensures a homogeneous distribution of the metal ions in its polymeric network structure and inhibits their segregation and/or precipitation from the solution.…”