Electrical and thermal investigations of the phase transition in sodium bicarbonate, NaHCO₃

Abstract

This paper reports on a structural phase transition in sodium hydrogen carbonate, NaHCO, as revealed by the investigations of some electrical and thermal parameters.Measurements of d.c. electric conductivity (a) and relative premittivity ( E ) of polycrystalline samples of NaHCO, as a function of temperature in the interval 300 c T < 400K reveal the existence of a structural phase transition around 365 K.Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were also performed in the same temperature range. The (DTA) results confirm the existence of a structural phase transition at r 3 6 5 K whereas the (TGA) results show the absence of any actual loss in weight in the transition temperature region.The data are correlated to the crystal structure including the hydrogen bonding system.

Phase Transitions in Some Hydrogen-Bonded Molecules

“…Such behavior strongly supports the existence of structural phase transition. It is known that the change in and/or the weakening of the hydrogen bonding are the primary cause of the structural phase transitions [3][4][5][6][7][8][9]. For example, the phase transition in ammonium sulphate (NH 4 ) 2 SO 4 is not of the order-disorder type but rather involves a change in the hydrogen bonding of the ammonium ion into sulphate ion, i.e.…”

“…The formation of hydrogen bond in a compound strongly modifies many physical properties because it alters the size, shape and arrangement of atoms as well as the electronic structure of the functional groups [2]. Recent studies clarified also that the H-bond is the main cause of the phase transition in some dielectric compounds [3][4][5][6][7][8][9]. Furthermore in some cases, ferroelectric properties are explained according to the behavior of the H-bond in crystals [10].…”

Thermal Analysis

“…Other studies involving nitrates include the combustion of Ti and Zr particles with KNO 3 (166) and the thermal decomposition of KNO 3 ‚6H 2 O (167). Sodium bicarbonate has been studied using various techniques of thermal analysis from a kinetic aspect (122), of kinetics combined with optical microscopy (168), and by a combination of electrical and thermal studies (169) tated under different conditions forms an hydroxy carbonate and has been the subject of thermal analysis investigations in the pure form (170) and in the presence of doped materials (171). The technique of CRTA has been applied to copper hydroxy carbonate (172).…”

Some aspects of electrical properties and structural phase transition inp-diiodobenzene

“…Over the last several years, and also at present, our research program is centered on the investigation of phase transition in some organic, inorganic and/or complex compounds [1][2][3][4][5][6][7] through the study of their electrical, calorimetric and/or thermal parameters at different temperatures. Most of the investigated compounds are hydrogen-bonded in their crystalline states.…”