US EPA

2839912 

Journal Article 

delta-KNO3: Synthesis and Structure of a New Modification of Potassium Nitrate 

Wolf, S; Alam, N; Feldmann, C 

2015 

1 

Zeitschrift fuer Anorganische und Allgemeine Chemie
ISSN: 0044-2313 

641 

2 

383-387 

10.1002/zaac.201400538 

WOS:000351444500039 

A novel modification of potassium nitrate is obtained subsequent to solvothermal reaction and crystallization at reduced temperature from diethylformamid (DEF) as solvent. delta-KNO3 crystallizes with the monoclinic space group P2(1)/c. Most intriguing is the coordination number of potassium and oxygen as expressed by the Niggli notation delta-K-8/8[NO4/4O4/2] that differs from the known modifications of potassium nitrate (alpha-K-9/9[NO9/3], beta-K-9/9[NO9/3], gamma-K-9/9[NO9/3]). Moreover, the stacking of the NO3- anions differentiates from the known KNO3 modifications. As only few crystals were obtained, the new modification is characterized by single-crystal structure analysis as well as by Fourier-transformed infrared spectroscopy. The latter reliably points to the presence of nitrate and shows a nu(N-O) vibration centered at 1384 cm(-1), but with significantly different shape and band width as compared to alpha-K-9/9[NO9/3] as a reference. 

Potassium nitrate; Synthesis; Crystal structure; Modification