Synthesis of Non-uniformly Pr-doped SrTiO₃ Ceramics and Their Thermoelectric Properties

The overall goal of this procedure is to synthesize non uniformly PIO Dium doped Strontium Titan eight ceramics with improved thermoelectric properties. This is accomplished by first preparing the PIO Dium doped strontium titanate powder by a high temperature solid state reaction with a series of intermediate grinding and mixing. The second step is to densify the prepared powder into bulk ceramic discs using a fast heating spark plasma centering technique.

The final step is to perform the measurements of thermal and electronic transport properties as a function of temperature on the centered ceramics. Ultimately, these electronic and thermal transport measurements are used to show the improvements in the thermal electric power factor and figure of merit. The main advantage of this technique over existing methods, such as reaction with conventional centering and heart pressing, is that significant improvement in carrier mobility and thermal electric power factor can be achieved using grain bound engineering by taking advantage of high heating rate capability of spark plasma syndrome techniques.

This method help answer questions in the field of thermal electric oxides and the field of electro ceramics, such as the potential of stratum titanate for high temperature thermal, electric power generation applications, as well as the modification electronic properties of this oxide. Though this method can provide insight into the thermal electric properties of STR titan it. It can also be applied for other systems such as electro ceramics for applications from solid oxide.

First cells, cel defer electricity, First weigh out stoic geometric amounts of strontium carbonate powder, titanium oxide, nano powder, and odium oxide centered lump grind. The odium oxide centered lumps to find particles using an agate mortar and pestle. Add the strontium carbonate powder and titanium oxide nano powder to the mortar and continue grinding and mixing until a visually homogenous powder is achieved.

Next, load the ground powder into a glass jar and mix. Using a turbulator for 30 minutes to homogenize the mixture. Ideally, a turbulator is the best choice, but if you need to, you can manually shake the glass for a couple of minutes.

When finished, load the resulting mixed powder into a meticulously cleaned and polished stainless steel dye and sandwich it between two stainless steel plungers. Then cold press the powder using a press under approximately one metric ton load when finished, place the pellet vertically in an Illumina boat filled with commercially purchased strontium Titan eight powder as the barrier between the Illumina boat and the cold press Pellet. Place the boat in a tube furnace heat up to 1300 degrees Celsius in three hours and keep it at this temperature for 15 hours.

After allowing the pellet to cool to room temperature inside the furnace, grind it using the agate mortar and pestle and load the resulting powder into a glass jar for further mixing. Using the turbulator, once the powder has been mixed, load it into the stainless steel dye and cold press under an approximately three metric tons of load. After heating at 1400 degrees Celsius in the tube furnace, grind the pellet using the agate mortar and pestle.

Then repeat the previous two steps one more time for the solid state reaction to reach completion. At this point, prepare circular graph oil pieces to cover the top and bottom interface of the sandwiched powder and graphite plungers in the graphite dye. Also, prepare another rectangular graph oil piece to cover the inner wall of the graphite dye.

Load 1.6 grams of the as prepared powder into a 12.7 millimeter inner diameter graphite dye and sandwich the powder between two graphite plungers of the same size. After cold pressing the powder wrap a piece of graphite felt around the dye for insulation and secure it with graphite yarn. Place the loaded graphite dye and plungers in the spark plasma centering or SPS chamber.

Move the stage to the final position. Then focus and align the porometer target circle on the temperature reading hole of the dye. Close the chamber and put a 7.7 kilo newton load on the sample.

Vacuum and purge the chamber with Argonne three times and leave the chamber under dynamic vacuum of six pascal. Next, increase the temperature by increasing the current manually. Once the temperature has been held at 1500 degrees Celsius for five minutes, shut the current off and quickly release the 7.7 kilo Newton load to avoid cracking the sample during the cooling down.

After allowing the sample to cool to room temperature inside the chamber, polish it using a 400 grid sandpaper down for 0.3 to 0.5 millimeters from each side to assure the complete removal of the graph oil. Then clean the sample with acetone. Determine the density of the ceramic disc using the Archimedes method by measuring the weight of the sample.

Then measure the weight of the sample submerged in water on a stabilized density measurement system, and calculate the Archimedes density using the following equation. After measuring the thickness of the sample using a digital micrometer, measure the thermal diffusivity of the sample using the transient laser flash technique under a 75 milliliter per minute flow of argonne. Calculate the thermal diffusivity by the laser flash interface software from the thickness of the sample and the temperature rise time profile using the Parker equation.

Following this, cut the disc pellet using a diamond saw into rectangular bars for electrical conductivity and C back coefficient measurements. A square disc for high temperature specific heat and a thin rectangular piece. For hall measurements, measure the specific heat of the sample on the flat and mirror polished square piece using a differential scanning calorimetry under argonne flow.

Next, calculate the high temperature thermal conductivity of the sample from the measured values of thermal diffusivity, the specific heat and the density using the following equation. Vision gold plate. The probes contact points on the two by two by 10 millimeter cubed piece cut from the sample to alleviate the contact resistance issues following this sputter and approximately 200 nanometer thick gold film using a benchtop gold sputtering unit.

When finished, measure the distance between these two probes using a digital microscope for electrical measurements. Then measure electrical conductivity using the four terminal method simultaneously measure the CBE C coefficient on the same setup using the measurements of temperature and voltage via the two middle thermocouple probes. Finally, measure the hall carrier concentration as a function of temperature on the eight by five by one millimeter cubed sample using a physical properties measurement system.

X-ray diffraction patterns. Confirm the formation of strontium titanate phase in all powders where the reflections can be indexed to a cubic lattice. With PM three bar M space group, weak reflections were observed corresponding to the intermediate predium oxide By optimizing the SPS heating rate, the secondary phase reflections disappear.

Electrical conductivity can be increased through the optimization of the heating rate, which is attributed to an enhancement in the carrier mobility. Since similar CEC coefficient and carrier concentration values were obtained for samples densified under different heating rates. Scanning electron micrographs show that the PIO dium rich secondary phase can partially dope the grain boundary region.

During the SPS process. By optimizing the heating rate, the grain boundary region can be fully doped and a carrier mobility enhancement is observed. All samples exhibit a degenerate semiconducting behavior for electrical conductivity and a corresponding diffusive like thermopower.

A large thermoelectric power factor greater than one was observed in a broad temperature range reaching a maximum of 1.3. A monotonic reduction in thermal conductivity was observed with increasing predium more than 30%improvement in the dimensionless thermoelectric figure of merit for the whole temperature range. Over previously reported maximum values were achieved as a result of the thermoelectric power factor enhancement and conductivity reduction.

Once mastered the spark plus mass centering of doped STR sim titan, it can be done in about 10 minutes with about an hour for cooling. After watching this video, you should have a good understanding of how to synthesize presidium dope ast Tanium Titan at v ceramics using salsa reaction and fast hitting spark plasma syndrome technique.