TY - JOUR
T1 - The structure and thermochemistry of K2CO3-MgCO3 glass
AU - Wilding, Martin C.
AU - Phillips, Brian
AU - Wilson, Mark
AU - Sharma, Geetu
AU - Navrotsky, Alexandra
AU - Bingham, Paul
AU - Brooker, Richard A
AU - Parise, John B
PY - 2019/10/14
Y1 - 2019/10/14
N2 - Carbonate glasses can be formed routinely in the system K2CO3-MgCO3. The enthalpy of formation for one such 0.55K2CO3-0.45MgCO3 glass was determined at 298 K to be 115.00 + 1.21 kJ/mol by drop solution calorimetry in molten sodium molybdate (3Na2O.MoO3) at 975 K. The corresponding heat of formation from oxides at 298 K is -261.12 + 3.02 kJ/mol. This ternary glass is shown to be slightly metastable with respect to binary crystalline components (K2CO3 and MgCO3) and may be further stabilized by entropy terms arising from cation disorder and carbonate group distortions. This high degree of disorder is confirmed by 13C MAS NMR measurements of the average chemical shift tensor values, which show asymmetry of the carbonate anion significantly larger than previously reported values. Molecular dynamics simulations show that the structure of this carbonate glass reflects the strong interaction between the oxygen atoms in distorted carbonate anions and potassium cations.
AB - Carbonate glasses can be formed routinely in the system K2CO3-MgCO3. The enthalpy of formation for one such 0.55K2CO3-0.45MgCO3 glass was determined at 298 K to be 115.00 + 1.21 kJ/mol by drop solution calorimetry in molten sodium molybdate (3Na2O.MoO3) at 975 K. The corresponding heat of formation from oxides at 298 K is -261.12 + 3.02 kJ/mol. This ternary glass is shown to be slightly metastable with respect to binary crystalline components (K2CO3 and MgCO3) and may be further stabilized by entropy terms arising from cation disorder and carbonate group distortions. This high degree of disorder is confirmed by 13C MAS NMR measurements of the average chemical shift tensor values, which show asymmetry of the carbonate anion significantly larger than previously reported values. Molecular dynamics simulations show that the structure of this carbonate glass reflects the strong interaction between the oxygen atoms in distorted carbonate anions and potassium cations.
UR - http://www.scopus.com/inward/record.url?scp=85072267434&partnerID=8YFLogxK
U2 - 10.1557/jmr.2019.250
DO - 10.1557/jmr.2019.250
M3 - Article (Academic Journal)
AN - SCOPUS:85072267434
SN - 0884-2914
VL - 34
SP - 3377
EP - 3388
JO - Journal of Materials Research
JF - Journal of Materials Research
IS - 19
ER -