Solid state sintering of very low and negative thermal expansion ceramics by Spark Plasma Sintering

Abstract

Lithium aluminosilicate powder precursors of compositions Li 2 O:Al 2 O 3 :SiO 2 as 1:1:2; and 1:1:3.11 were synthesized and sintered by the Spark Plasma Sintering technique. The sintering conditions were adjusted to obtain dense ceramic materials in an attempt to avoid the presence of a glassy phase. XRD and SEM images were employed for composition and microstructure characterization. The coefficient of thermal expansion of the sintered samples was studied down to cryogenic conditions. Rietveld quantification was performed with the use of an external standard. Pure beucryptite of different compositions in dense ceramic bodies was obtained with a negative expansion coefficient. #

Thermal expansion of β-eucryptite in oxide-based ceramic composites

“…46 Thus, compositional changes that can be induced by sintering could be also responsible for the E-CTE modification. 47 Based on these previous results, it is clear that further work is necessary to determine if the modification of the ␤-eucryptite lattice parameters, when it is presented in well-densified AE and ZE composites, is only due to the deformation of the ␤-eucryptite cell, to other factors (order-disorder transformation or compositional changes) or a combination of them.…”

Fabrication of near-zero thermal expansion of fully dense β-eucryptite ceramics by microwave sintering

“…To overcome the problem of grain growth, non-conventional sintering methods, have emerged as promising techniques [11].…”

Comportamiento de la eucriptita a alta temperatura mediante estudio <i>in situ</i> por difracción de Rayos X

“…Este cambio de signo en torno a 250 ºC ha sido también observado en otros trabajos con esta composición (6,19) y su interpretación debe estar relacionada con los cambios en los parámetros a y c con el aumento de la temperatura en la estructura ordenada, que es la que predomina en ese rango de temperaturas.…”

“…El α volumétrico de la β-eucriptita es negativo en un amplio rango de temperaturas siendo incluso positivos los valores de α a y α b , debido a que posee un α c con valores muy negativos. Estudios previos sobre las propiedades dilatométricas de la β-eucriptita han sido publicados por los autores del presente trabajo (5,6). En dichos trabajos se ha puesto de manifiesto la necesidad de estudiar de manera más profunda la relación entre las propiedades térmicas y la estructura y composición cristalina en los materiales LAS.…”