1. Synthesis and Properties of Sodium Oxy-thio-Phosphate Glasses
Adriana Joyce
Glass and Optical Materials Group Materials Science and Engineering
Hi, I’m Adriana Joyce, a sophomore in Materials Engineering.
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2. Most of the glass you see in everyday life is either soda-lime glass, made of sodium carbonate( not to be confused with baking soda, or sodium BI carbonate) and a combination of silicon, aluminum, and sodium oxides or borosilicates, boron and silicon based glasses. Soda lime glass is the most common, used in windows and glassware. Borosilicates, which you’ll recognize in the popular brand Pyrex, have a very low coefficients of thermal expansion, which make them perfect for the rapid temperature changes that are inherent to cooking and lab work. You’ve probably heard of glass as an electrical insulator, which those two types of glass are indeed good at. However, there are other uses for glass, and I‘m going to focus on the exploration of the properties and structures of a type of glass that conducts ions as an electrolyte for large, rechargeable batteries, like those used for renewable energy sources, say, windmills. The project I’m working on is centered around using sodium based glasses, and this series also contains phosphorus, sulfur, and oxygen. Adding oxygen incrementally increases the electronegativity of the glass, and I’ll cover the physical properties and structural changes this causes.
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3. Abundance in earths crust Lithium 0.0017% Sodium 2.3%
The majority of rechargeable batteries in use right now have a liquid electrolyte (the yellow, here) between the electrodes. However, this poses a large danger because the liquid electrolyte allows for the growth of dendrites *point* which short the cell and can cause fire and explosions, which isn’t a good selling point. So, to prevent these dendrites from forming, research is being done to develop solid electrolytes, in this case, solid, glassy electrolytes. As I mentioned, this particular series uses sodium. Na is 230% more abundant than the more commonly used lithium, which makes it cheaper. So, a glass has to be developed to be a good ion conductor AND easily processable for large scale manufacturing if these batteries are to be successful.
Wu, H., Zhuo, D., Kong, D., & Cui, Y. (2014, October 13). Improving battery safety by early detection of internal shorting with a bifunctional separator. Retrieved March 24, 2017, from
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4. Synthesis Planetary Milled (PM) Glasses
Fritsch PULVERSITTE 6 Planetary Mono Mill
450 rpm
20 hours
67Na2S + 33[(x)P2S5 + (1-x)P2O5]
This glass series was synthesized using a planetary mill. This planetary mill uses a zirconia mill pot and 15 zirconia mill balls, zirconia, because it’s non-reactive with the very corrosive sulfur. It rotates at very high speed, and uses the energy created by the milling media colliding to instantaneously melt and react the compounds. The continual rotation of the milling media and mill pot create a homogenous, reacted mixture.
Not only does the planetary mill produce amorphous materials, but it is easily scaled for producing large volumes. The powders are combined in the mill pot with the milling media and pummeled for 20 hours at 450 rpms. The high energy collisions force chemical reactions to happen as the different powders are crushed together at high speed.
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5. 67Na2S + 33[(x)P2S5 + (1-x)P2O5] X-Ray Diffraction
All compositions are glassy
X=1.0
After synthesis, the samples were tested for glassiness. The broad peaks found by X-Ray Diffraction show all the compositions to be amorphous.
X=0.0
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6. Infrared Spectroscopy
P1 oxygen P2
PO3 terminating groups P1
P0 Oxygen
P0 Sulfur
Infared Spectroscopy measures the vibrations of atoms caused by the absorption of infrared light. This, combined with other spectroscopy techniques, allows us to determine the structural units present in the glass. Here I have highlighted the peaks and their corresponding structures. I’ll explain the structures in the next slides, but you can see here how those peaks increase and decrease as the composition changes. The P1 oxygen structures increase as the oxygen concentration increases. The p2’s also increase as the oxygen concentration increases, due to the higher tendency for oxygen, over sulfur, to form bridging bonds and long chains. As the chains increase, so do the number of chain ends, the terminating PO3 units, in yellow. As the bridging sulfur (P1, in green) gets replaced by oxygen, it forms non bridging P0 units, which is why the concentration of those increases even as the sulfur concentration decreases.
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7. Structural Changes Across
67Na2S + 33[(x)P2S5 + (1-x)P2O5]
P2S7 P1 P2
P0 Sulfur
When x is equal to 1, the sulfide end, most of the glass is made up of the p1 structure. P1, in that there is one bridging sulfur per phosphorus atom. Now, the force of the planetary milling breaks the double p1 units into two separate p1 units and, eventually, into the more thermodynamically stable p2s, two bridging sulfurs and p0 units, no bridging sulfurs. This is at the P2S7 composition. Then oxygen gets added into the mix.
Balema, Viktor P., Dr. "Mechanical Processing in Hydrogen Storage Research and Development." Sigma-Aldrich. Sigma Aldrich, n.d. Web. 21 Mar <
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8. Structural Changes Across
67Na2S + 33[(x)P2S5 + (1-x)P2O5]
P0 Oxygen
P1 oxygen
As oxygen is added, the sulfurs are slowly replaced, moving from P2S7 to P2S6O, P2S5O2 and so forth until x=0 and the composition is P2S2O5. Oxygen is most stable as a bridging atom initially because P-O-P bonds are much stronger and more thermodynamically favorable than the P-S-P bonds. So, first the p1 units form with a bridging oxygen, P2S6O. As more oxygen is added, it transitions to chains of these structures, with oxygen still as the bridging atom. As the oxygen concentration increases further, oxygen replaces the other sulfurs, forming additional PO4 units, and PO3 units. The glass former, sodium sulfide, still provides sulfur atoms, and those collect in Na3PS4 units, which don’t bridge, and break up the glass network, which lowers the working range of the glass. The working range is the temperature difference between the glass transition temperature and crystallization. This is the range where the glass can be processed, so the larger the better.
P0 Sulfur
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9. Thermal Properties
The samples were tested in aluminum pans in a Diamond DSC to determine the glass transition and crystallization temperatures.
The glass transition temperature (Tg) is determined in differential scanning calorimetry, or DSC, where the heat flow is measured as a function of temperature. The Tg is the point where the glass goes from being a solid to a very viscous liquid, and is noticeable as the upward change in angle before the crystallization peak. First, a survey scan is run from 50 to 450C to determine the glass transition and crystallization temperatures. Then, a cycling scan is run, from 50 to 4 temperatures above the Tg confirm the temperatures.
The Tg, in black, generally increases as X goes from 1 to 0, sulfide to oxy-sulfide. This is due to the oxygen chains forming strong bonds and increasing the networking of the glass. As oxygen is added, the oxygen chains force the sulfur to form Na3PS4 units, which are non-bridging units, they break up the network and decrease the Tg *here*
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10. Conductivity
Conductivities tested using a 13mm diameter powder compact pellet with silver paint electrodes
The conductivities of these glasses were tested using a small, airtight cell that allowed for a powder compact pellet to be inserted and a current run through it. The pellets were about a mm thick and 13 mm in diameter. The density of the pellet was dependent on the pressure the pellets were pressed at and, when tested, higher density pellets have better conductivities. All the pellets in this series were pressed at similar pressures, the highest possible without destroying the pellet. Conductive silver paint was applied to either side of the pellet to act as electrodes in the cell. The conductivities were tested on the NovoControls scanning from 1E7-1E-1 Hz and from C, twice. The second cycle usually produced a higher conductivity, due to relaxation of the highly stressed powder and the sintering of the grains in the powder. The highest conductivities were found to be at the S end, due to the presence of Na3PS4 crystallinity, but with the inclusion of oxygen, the oxy-sulfides at x=0.8, P2S6O had the best conductivity, when the oxygen chains are most present and give the sodium a highway to be conducted along. As more oxygen is added, more Na3PS4 and PO4 units form, breaking up the conducting chains.
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11. Results
P1 units are milled into P0 and P2 units at high sulfur concentrations.
The addition of oxygen creates P-O-P bonds that are more thermodynamically stable than P-S-P bonds
P-O-P bonds form ion conducting chains that increase conductivity and networking
Future Work
Increasing conductivity by exploring the addition of other elements
Balance working range and conductivity for processability
Now that the structures of this series are better understood, they can be used to understand the structures of other glass series. The transition from P1 units to P0 and P2, the phosphorus oxygen phosphorus chains, and the PS4 and PO4 units that break up the network and decrease conductivity have been identified. By marking those peaks in the IR data, and noting the effects of the addition of oxygen for the tg and tx, it will be easier to find the next composition to explore. A composition with higher conductivity, and just enough networking to be easily processable.
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12. Acknowledgements Dr. Steve Martin Steven Kmiec
Iowa State University Glass and Optical Materials Group
ArpaE Grant DE-AR
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13. Questions ajoyce@iastate.edu Iowa State University