PMID- 26618389
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20160425
LR  - 20151224
IS  - 1520-5207 (Electronic)
IS  - 1520-5207 (Linking)
VI  - 119
IP  - 51
DP  - 2015 Dec 24
TI  - Composition Dependence of the Na(+) Ion Conductivity in 0.5Na2S + 0.5[xGeS2 + (1 
      - x)PS5/2] Mixed Glass Former Glasses: A Structural Interpretation of a Negative 
      Mixed Glass Former Effect.
PG  - 15738-51
LID - 10.1021/acs.jpcb.5b07383 [doi]
AB  - A negative mixed glass former effect (MGFE) in the Na(+) ion conductivity of 
      glass has been found in 0.5Na2S + 0.5[xGeS2 + (1 - x)PS5/2] glasses where the 
      Na(+) ion conductivity is significantly smaller for all of the ternary glasses 
      than either of the binary end-member glasses. The minimum conductivity of  approximately 0.4 x 
      10(-6) (Omega cm)(-1) at 25  degrees C occurs for the x = 0.7 glass. Prior to this 
      observation, the alkali ion conductivity of sulfide glasses at constant alkali 
      concentration, but variable ratio of one glass former for another (x) ternary 
      mixed glass former (MGF) glasses, has always produced a positive MGFE in the 
      alkali ion conductivity; that is, the ternary glasses have always had higher ion 
      conductivities that either of the end-member binary glasses. While the Na(+) ion 
      conductivity exhibits a single global minimum value, the conductivity activation 
      energy exhibits a bimodal double maximum at x  approximately  0.4 and x  approximately  0.7. The modified 
      Christensen-Martin-Anderson-Stuart (CMAS) model of the activation energies 
      reveals the origin of the negative MGFE to be due to an increase in the 
      dielectric stiffness (a decrease in relative dielectric permittivity) of these 
      glasses. When coupled with an increase in the average Na(+) ion jump distance and 
      a slight increase in the mechanical stiffness of the glass, this causes the 
      activation energy to go through maximum values and thereby produce the negative 
      MGFE. The double maximum in the conductivity activation energy is coincident with 
      double maximums in CMAS calculated strain, DeltaES, and Coulombic, DeltaEC, activation 
      energies. In these ternary glasses, the increase in the dielectric stiffness of 
      the glass arises from a negative deviation of the limiting high frequency 
      dielectric permittivity as compared to the binary end-member glasses. While the 
      CMAS calculated total activation energies DeltaEact = DeltaES + DeltaEC are found to 
      reproduce the overall shape of the composition dependence of the measured DeltaEact 
      values, they are consistently smaller than the measured values for all 
      compositions x. The new concept of an effective Madelung constant for the Na(+) 
      ions in glass is introduced, MD(Na(+)), to account for the difference. Calculated 
      MD(Na(+)) values necessary to bring the CMAS and experimental DeltaEact values into 
      agreement are in excellent agreement with nominal values for typical oxide 
      crystals containing Na(+). New MD simulations of oxide glasses were performed and 
      were used to calculate MD(Na(+)) values for Na2O + SiO2 glasses for the first 
      time and were found to agree quite well with the values for the sulfide glasses 
      studied here. Insights from the current study have been used to predict and 
      design new MGF systems that may lead to a positive MGFE in the ionic 
      conductivity.
FAU - Martin, Steve W
AU  - Martin SW
AD  - Department of Materials Science and Engineering, Iowa State University , Ames, 
      Iowa 50010-2300, United States.
FAU - Bischoff, Christian
AU  - Bischoff C
AD  - Department of Materials Science and Engineering, Iowa State University , Ames, 
      Iowa 50010-2300, United States.
FAU - Schuller, Katherine
AU  - Schuller K
AD  - Department of Materials Science and Engineering, Iowa State University , Ames, 
      Iowa 50010-2300, United States.
LA  - eng
PT  - Journal Article
PT  - Research Support, U.S. Gov't, Non-P.H.S.
DEP - 20151215
PL  - United States
TA  - J Phys Chem B
JT  - The journal of physical chemistry. B
JID - 101157530
EDAT- 2015/12/01 06:00
MHDA- 2015/12/01 06:01
CRDT- 2015/12/01 06:00
PHST- 2015/12/01 06:00 [entrez]
PHST- 2015/12/01 06:00 [pubmed]
PHST- 2015/12/01 06:01 [medline]
AID - 10.1021/acs.jpcb.5b07383 [doi]
PST - ppublish
SO  - J Phys Chem B. 2015 Dec 24;119(51):15738-51. doi: 10.1021/acs.jpcb.5b07383. Epub 
      2015 Dec 15.