Effect of secondary thermal treatment on crystallinity of spinel-type Co(Cr,Al)2O4 pigments synthesized by solution combustion route

Abstract

The effect of a post-synthesis thermal treatment on CoCr 2-2Y Al 2Y O 4 (0.0≤Y≤1.0) ceramic pigments synthesized by Solution Combustion Synthesis (SCS) has been studied. Assynthesized SCS pigments were treated at two different calcination temperatures (800 ºC and 1000 ºC) to study changes in mineralogy, microstructure and thermal behaviour, as well as their effect over the colouring power. Spinel-type Fd-3m crystalline structure was developed in all cases. Nevertheless, crystallinity parameters were highly affected by both analysed processing parameters: composition (Y) and post-synthesis calcination temperature (T c). A Cr(III) enrichment along with T c increase favoured ion rearrangement to promote sample crystallization and crystallite growth. Fast kinetics of SCS makes Al-rich spinels with transition metals difficult to be synthesized. The application of a secondary thermal treatment resulted in a favourable evolution towards a well-crystallized structure. Lattice parameter did not seem to be affected by T c , although it evolved indeed with composition. From a microstructural point of view, as-synthesized pigments were foamy, with a very low bulk density and nanometric grain size. After the thermal treatment, larger grain sizes were obtained, especially for the samples richer in Al and treated at higher T c. All pigments developed intense colours in a transparent glaze without showing heterogeneities, indicating a stable behaviour against glazing process. Glaze colour evolved from green to perfectly blue shades, indicating an important dependence on composition. Nevertheless, colouring power seemed to be rather affected by calcination process.

Structure, microstructure, optical and magnetic properties of cobalt aluminate nanopowders obtained by sol-gel process

“…Cobalt aluminate spinel(CoAl 2 O 4 ) is known for its blue colour and it is widely used as pigment.s for ceramics, paint.s, fibres and so on. Among its advantages, this compound presents high thermal and excellent chemical stability [7][8][9][10]. The spinel oxides powders are generally prepared by solid state reactions [ll,12].…”

Investigation into Pigmentation Behaviors and Mechanism of Pigment Yellow 180 in Different Solvents

“…Among the synthetic organic pigments, azo pigments are gradually taking over the field of red and yellow pigments; more than 80% of yellow and 65% of red pigments have azo-linkages [3]. However, pigments generally do not achieve the target color after synthesis and usually require some post-treatment methods such as heating the pigment in water or organic solvents (suspensions), solvent grinding or ball milling [4,5], supercritical antisolvent process (CO 2 ) [6], and calcination [7]. These posttreatments are generally used for achieving crystallinity and increasing the crystallinity to obtain the desired color, hue, color strength, and hiding power.…”

Bright Structural Color and High Hydrophobic Properties of Photonic Crystal Films on the Ceramic Glaze Layer via Vertical Deposition Self‐Assembly Method

“…Traditional ceramic colored glaze often adds different metal ions according to the need of color such as adding copper ions to show red, adding cobalt ions to appear blue, [1][2][3][4][5] which will lead to the introduction of toxic and harmful ingredients and an increase of the production cost. [6][7][8][9] Simultaneously, some ceramic colored glazes face immense difficult problems by virtue of complex ingredients, different sintering atmospheres or temperatures and other factors, which strongly impacts the color of products.…”