Dilatometric studies of (SiO2-RE2O3-Al2O3) silicon carbide ceramics

Abstract

Silicon carbide is an important structural ceramic and finds applications as abrasives, as a refractory and in automotive engine components. This material can attain high densities during liquid phase sintering if suitable additives are used. Silicon carbides containing silica, alumina and rare earth oxides have suitable characteristics to promote liquid phase sintering. In this paper, the sintering behavior of silicon carbide ceramics with additives based on the (SiO 2 -RE 2 O 3 -Al 2 O 3 ) system (RE = Y, Dy) has been studied. Samples with different compositions and containing 90 vol.% SiC were sintered in a dilatometer at 1950 °C/1h and in a graphite resistance furnace from 1500 °C/1h up to 1950 °C/1h. The shrinkage behavior as a function of rare earth oxide used and additive composition was also studied. The sintered materials were characterized by density and weight loss measurements. The crystalline phases were identified by X-ray diffraction analysis. The sintering kinetics of these materials can be related to the formation of secondary crystalline phases.

Characterization of rare earth aluminosilicate glasses

“…We observed in another paper [22] that the existence of only one range of maximum shrinkage rate due to solution reprecipitation process is related to the fact that these compositions are located in the glass forming region, and, consequently, to the absence of secondary crystalline phases, which are an obstacle to the solution reprecipitation process. In this study, we observed that samples containing lanthania or neodimia as additives have extra ranges of maximum shrinkage rate (Fig.…”

“…These phases can dissolve into the liquid, and can disappear or crystallize as other phases, such as rare earth aluminum rich phases [23]. These phases are responsible for hindering the solution-reprecipitation process [22]. Samples containing yttria, dysprosia and ytterbia have only one range of maximum shrinkage rate due to a solution-reprecipitation process, and, probably, no transient secondary crystalline phases.…”

Dilatometric behaviour of doped barium titanate ceramic

“…The information about phase transitions in materials, sintering behavior, thermal expansion coefficients and their anisotropies have been obtained from this technique. During a solid state reaction, phases of different densities appear intermittently [19][20][21]. Also large-scale diffusion of ions can lead to microstructural reorganization of grains leading to fine particle intermediates and hence large dimensional change can occur [1].…”

“…Our earlier reported work on BZT has been focused on study of its structural, dielectric, relaxor, ferroelectric, piezoelectric and impedance spectroscopy properties etc [15][16][17]. In present paper, we studied a dilatometric thermal expansion measurement which generally deals with material properties such as lattice dynamics, electronic and magnetic interactions, thermal defects and phase transitions etc [18][19][20][21].…”