Synthesis and thermal stability study of cobalt hydroxynitrate in different polytypic modifications

Abstract

Cobalt hydroxysalt exists in Co(OH)(NO 3 ), Co 2 (OH) 3 (NO 3 ), Co 3 (OH) 4 (NO 3 ) 2 and Co 7 (OH) 12 (NO 3 ) 2 compositions. Co 2 (OH) 3 (NO 3 ) has been prepared by varying the experimental conditions. The X-ray powder diffraction patterns of Co 2 (OH) 3 (NO 3 ) obtained by different methods exhibit significant changes in their peak positions and the relative intensities. Careful analysis of the X-ray powder diffraction patterns of Co 2 (OH) 3 (NO 3 ) samples reveals that it can crystallize in different polytypic modifications. The thermal decomposition studies show that the Co 2 (OH) 3 (NO 3 ) of 3R 2 polytype has better structural stability compared to Co 2 (OH) 3 (NO 3 ) of 1H polytype. Co 2 (OH) 3 (NO 3 )-I and Co 2 (OH) 3 (NO 3 )-II has been prepared by two different methods and they crystallizes in 3R 2 and 1H polytypic modifications. The thermal decomposition studies show that Co 2 (OH) 3 (NO 3 )-I of 3R 2 polytype is structurally more stable compared to Co 2 (OH) 3 (NO 3 )-II of 1H polytype. ► Co 2 (OH) 3 (NO 3 ) has been prepared by varying the experimental conditions. ► The X-ray powder diffraction patterns of Co 2 (OH) 3 (NO 3 ) obtained by different methods exhibit significant changes in their peak positions. ► X-ray powder diffraction pattern analyses of Co 2 (OH) 3 (NO 3 ) samples reveal that they crystallize in 3R 2 and 1H polytypes. ► Co 2 (OH) 3 (NO 3 )-3R 2 polytype has better thermal stability compared to Co2(OH)3(NO3) of 1H polytype.