Production and Study of Ca/Sn(II) Metastable Fluoride Ion Conductors

1997 ◽  
Vol 481 ◽  
Author(s):  
Michael F. Bell ◽  
Georges Dénès ◽  
Zhimeng Zhu
Keyword(s):  
Solid Solution ◽  
Electrical Conductivity ◽  
High Temperature ◽  
Calcium Nitrate ◽  
Fluoride Ion ◽  
Conductivity Measurements ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Density Measurements ◽  
Ion Conductors

ABSTRACTPrecipitation reactions from aqueous solutions of calcium nitrate and tin(II) fluoride result in the formation of two metastable phases, depending on the reaction conditions. Crystalline CaSn2F6 and the microcrystalline Ca1-xSnxF2 solid solution are obtained, the latter crystallizing in the cubic fluorite (CaF2) type with total Ca/Sn disorder. Both phases are fluoride ion conductors. Electrical conductivity measurements versus temperature and bulk density measurements show that both phases are far from thermodynamic equilibrium at ambient conditions, and thus are metastable. Both decompose to a mixture of SnF2 and CaF2 at high temperature. In addition, CaSn2F6 is chemically unstable in an aqueous medium, in which it looses SnF2 to give the microcrystalline Ca1-xSnxF2 solid solution.

Electrical conductivity measurements of periclase under high pressure and high temperature

2010 ◽  
Vol 405 (1) ◽  
pp. 53-56 ◽  
Author(s):  
Xiaoping Wu ◽  
Baohua Zhang ◽  
Junshan Xu ◽  
Tomoo Katsura ◽  
Shuangmeng Zhai ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
High Pressure ◽  
High Temperature ◽  
Conductivity Measurements

Test Rig for High-Temperature Thermopower and Electrical Conductivity Measurements

2013 ◽  
Vol 42 (7) ◽  
pp. 1319-1323 ◽  
Author(s):  
S. Boldrini ◽  
A. Famengo ◽  
F. Montagner ◽  
S. Battiston ◽  
S. Fiameni ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
High Temperature ◽  
Conductivity Measurements ◽  
Test Rig

Phase Transitions in Lead(II) Fluoride Upon Milling

1997 ◽  
Vol 481 ◽  
Author(s):  
Georges DÉnÉ ◽  
M. Cecilia Madamba
Keyword(s):  
Activation Energy ◽  
Phase Transitions ◽  
High Temperature ◽  
High Temperature Phase ◽  
Fluoride Ion ◽  
Temperature Phase ◽  
Ambient Conditions ◽  
Ion Conductor ◽  
Frenkel Defects ◽  
High Temperature Polymorph

ABSTRACTPbF2 is known to exist under two different polymorphic structures. Orthorhombic α-PbF 2 is stable at ambient temperature. It has the PbC12 structure. Cubic β-PbF2 is obtained by heating α-PbF2. It does not transform back to α-PbF2 on cooling, and it seems to be infinitely stable in the metastable state under ambient conditions. β-PbF2 crystallizes in the fluorite (CaF2) type. Owing to the large number of potential interstitial sites, many F- Frenkel defects can be formed, which make β-PbF2 the highest performance fluoride ion conductor among binary fluorides. In this work, both phases of PbF2 have been ball milled. Milling α-PbF2 results in a partial transformation to microcrystalline β-PbF2. The energy required for obtaining the high temperature phase is probably provided in the mechanical form. Milling β-PbF2 leads to partial amorphization and formation of α-PbF2. In this case, milling transforms the high temperature polymorph to the low temperature form, by providing the energy required to overcome the activation energy that keeps PbF2 trapped in the high temperature β-form after cooling.

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