Name: Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties (Video) | JoVE Journal
Uploaded: 2015-08-15T14:00:00.000+00:00
Duration: 11 min 7 s
Description: Learn to synthesize Pr-doped SrTiO3 ceramics using solid-state reaction and spark plasma sintering for enhanced thermoelectric performance. This method improves carrier mobility and reduces thermal conductivity significantly.

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5 minutes

The authors wish to acknowledge the competitive faculty-initiated collaboration (FIC) grant from KAUST.

1. Preparation of Pr-doped SrTiO3 Powder
<ol>
	<li>In order to prepare 10 g of Sr0.95Pr0.05TiO3 powder, weigh the stoichiometric amounts of SrCO3 powder (7.53407 g), TiO2 nanopowder (4.28983 g), and Pr2O3 sintered lump (0.44299 g) following the reaction for x = 0.05:</li>
</ol>
<img alt="Static equilibrium chemical equation: (1-x)SrCO₃ + (x/2)Pr₂O₃ + TiO₂ → Sr₁₋ₓPrₓTiO₃₋δ + (1-x)CO₂." fo:content-width="5in" src="/files/ftp_upload/52869/52869eq1.JPG" width="550" data-altupdatedat="1787630408000" data-alt="Equation 1">
<ol start="2">
	<li>Grind the weighed Pr2O3 sintered lumps to fine particles using an agate mortar and pestle.</li>
	<li>Add the weighed SrCO3 powder and TiO2 nanopowder to the Pr2O3 and continue grinding and mixing using an agate mortar and pestle until a visually homogenous powder is achieved.</li>
	<li>Load the ground powder into a glass jar and mix using a turbulator for 30 min to homogenize the mixture.</li>
	<li>Load the resulting mixed powder into a meticulously cleaned and polished stainless steel die (1 inch in diameter) and sandwich it between two stainless steel plungers.</li>
	<li>Cold press the powder using a press under an approximately 1 metric ton load.</li>
	<li>Eject the cold-pressed pellet by placing the die on a hollowed stainless steel cylinder and pushing the plungers and the pellet out from the top using a pushing rod. Upon ejection of the cold pressed pellet (green body) from the die, clean any contamination on the circumferential surface of the pellet by gently covering the pellet with a small piece of scotch-tape and removing a thin layer by ripping the tape.</li>
	<li>Place the pellet vertically in an alumina boat filled with commercially purchased SrTiO3 powder as the barrier between the alumina boat and the cold press pellet.</li>
	<li>Place the boat in a tube furnace, heat up to 1,300 °C in 3 hr and keep it at this temperature for 15 hr. Allow the pellet to cool down to RT inside the furnace when the calcination is over. This step is referred to as the “calcination process” thereafter.</li>
	<li>Grind the pellet using the agate mortar and pestle and load the resulting powder into a glass jar for further mixing using the turbulator.</li>
	<li>Load the powder into the stainless steel die and cold pressed under an approximately 3 metric tons of load.</li>
	<li>Repeat the step 1.9 one more time at 1,400 °C in 3 hr and keep it at this temperature for 20 hr.</li>
	<li>Grind the pellet using the agate mortar and pestle.</li>
	<li>Repeat steps 1.11, 1.12, and 1.13 one more time for the solid state reaction to reach completion.</li>
</ol>
2. Preparation of Bulk Polycrystalline Pr-doped SrTiO3 Ceramic
<ol>
	<li>Weigh 1.6 g of the as-prepared powder (for a disk 2 mm thick and 12.7 mm in diameter).</li>
	<li>Prepare circular graphoil pieces to cover the top and bottom interface of the sandwiched powder and graphite plungers in the graphite die. Also, prepare another rectangular graphoil piece to cover the inner wall of the graphite die.</li>
	<li>Load the as-prepared powder into a graphite die (12.7 mm in inner diameter) and sandwich the powder between two graphite plungers of the same size. Drill a 2-mm hole in the middle of the length of the graphite die and from the outer surface of the die to about 2 mm of the inner surface for temperature reading. 
	Note: Adjust the length of the graphite plungers remaining outside the die and position the center of the sandwiched powder cylinder where the hole is placed to get an accurate temperature reading. The faces of the graphite plungers need to be meticulously leveled during the machining of the pieces. Any misalignment can result in the cracking of the sintered pellet during spark plasma sintering.</li>
	<li>Cold-press the powder gently (load &lt; 200 kg) using a press prior to mounting on the spark plasma sintering plate inside the chamber. Use flat polished stainless steel support plates between the top and bottom plungers and the press stage to avoid damaging the graphite plungers.</li>
	<li>Wrap a piece of graphite felt around the die for insulation and secure it with graphite yarn. Devise a window on the graphite felt by cutting a rectangular piece of the felt where the temperature reading hole is placed on the die.</li>
	<li>Place the loaded graphite die and plungers in the spark plasma sintering chamber. Move the stage to the final position.</li>
	<li>Focus and align the Pyrometer target circle on the temperature reading hole of the die. Make sure the emissivity setting of the pyrometer is set for graphite.</li>
	<li>Close the chamber and put a 7.7 kN load (approximately 60 MPa) on the sample. Vacuum and purge the chamber with Ar three times and leave the chamber under dynamic vacuum of 6 Pa.</li>
	<li>Increase the temperature by increasing the current (manually or using a program). Use 250 A min-1 (corresponding to approximately 300-400 °C min-1) for the optimized samples. This is the most important step of the spark plasma sintering process.</li>
	<li>Keep the temperature at 1,500 °C for 5 min by manually adjusting the current or using the program. At the end of the 5 min holding period, shut the current off and quickly release the 7.7 kN load to avoid cracking the sample during the cooling down. Let the sample cool to RT inside the chamber.</li>
	<li>Release the bulk pellet from the graphite die gently using the cold press. This is done by placing the graphite die on a hollowed steel cylinder and ejecting the pellet and the graphite plungers using a steel pushing rod from the top.</li>
	<li>Remove the graphoil on top and bottom faces of the pellet as well as the circumferential surface using a sharp razor blade.</li>
	<li>Polish the sample using a rough sand paper (400 grid) down for 0.3-0.5 mm from each side to assure the complete removal of the graphoil. Clean the sample with acetone.</li>
</ol>
3. Characterization of Electronic and Thermal Transport Properties of Bulk Ceramics
<ol>
	<li>Determine the density of the ceramic disk, ρ, using the Archimedes method.</li>
	<li>Measure the weight of the sample, Wdry, and then the weight of the sample submerged in water, Wwet, on a stabilized density measurement system and calculate the Archimedes density from</li>
</ol>
<img alt="Density formula; ρ = Wdry/(Wdry-Wwet)×ρwater; equation in material science diagram." fo:content-width="2.1in" src="/files/ftp_upload/52869/52869eq2.JPG" width="260" data-altupdatedat="1787630408000" data-alt="Equation 2">
where ρwater is the density of the water at the measurement temperature (e.g., equals 1 g cm-3 at 300 K).14
<ol start="2">
	<li>Measure the thermal diffusivity of the sample, d, using the transient laser-flash technique under a 75 ml min-1 flow of Ar. Measure the thickness of the sample, L, accurately first using a digital micrometer. 
	Note: Parallel-faced samples with different sizes and shapes (e.g., round discs 12.7 mm in diameter or square 10 x 10 mm2 disks) and thicknesses between 0.5 and 5 mm can be easily measured.
	<ol>
		<li>In the laser-flash thermal diffusivity technique, irradiate one face of the sample by a short (~1 msec) laser pulse and record the temperature rise on the opposite face by an infra-red detector. Then calculate thermal diffusivity by the laser-flash interface software from the thickness of the sample and the temperature rise-time profile using the Parker equation15</li>
	</ol>
	</li>
</ol>
<img alt="Diffusion equation d=0.138(L²/t₁/₂); formula." fo:content-width="1.9in" src="/files/ftp_upload/52869/52869eq3.JPG" width="220" data-altupdatedat="1787630408000" data-alt="Equation 3">
where L is the thickness of the disk and t1/2 is the half-time of the maximum temperature rise of the other side of the sample.
Note: The Parker model15 assumes ideal conditions of adiabatic sample and instantaneous pulse heating, other models have been proposed over the years, which account for various losses in the measurement such as heat losses, finite pulse duration, non-uniform pulse heating and nonhomogeneous structures. We have used the Cowan model16 with pulse correction which is one of the most advanced methods. It should be noted that in order to maximize the amount of thermal energy transmitted from the front surface and to maximize the signal observed by the IR detector, the sample surfaces must be highly emissive. Usually this requires the application of a thin coating of graphite to the sample surfaces. An uncertainty of 2%-5% in the measurement of thermal diffusivity exists, arising from the determination of dimension.17
<ol start="3">
	<li>Cut the disk pellet using a diamond saw into rectangular bars, 2 x 2 x 10 mm3, electrical conductivity and Seebeck coefficient measurements as well as a square disk, 4 x 4 x 1.5 mm3 for high-temperature specific heat and a thin rectangular piece, 8 x 5 x 1 mm3 for Hall measurements.</li>
	<li>Measure the specific heat, Cp, of the sample on the flat and mirror-polished square piece (4 x 4 x 1.5 mm3) using a differential scanning calorimetry (DSC) under argon flow.18
	<ol>
		<li>Use a heating rate of 5 K min-1 up to 40 °C for an isothermal hold for 10 min to allow the sample to reach thermal equilibrium followed by 20 K min-1 heating rate up to 500 °C, with an exact cooling rate which followed. Perform the measurement under the flow of argon (50 ml min-1 is suggested).</li>
	</ol>
	</li>
</ol>
Note: Due to the sensitivity of the method used for analysis, conduct three measurements to determine the heat capacity including (1) a baseline measurement to subtract the background, (2) measurement of the specific heat of a standard material (such as sapphire) with a known CP, and (3) measurement of the specific heat of the sample. Ensure that samples are flat and mirror-polished in order to make an ideal contact with the bottom of the measurement crucible (Pt/Rh pans with Al2O3 crucibles used in this work). More details on the exact structure of the DSC stage, a comparison of the DSC techniques to others, and exact instructions for measuring a sample can be found in various sources.19
<ol start="5">
	<li>Calculate the high-temperature thermal conductivity, κ, of the sample from the measured values of thermal diffusivity, d, the specific heat, CP, and the density, ρ using20</li>
</ol>
<img alt="Thermal conductivity equation κ=ρdCp; formula for heat transfer analysis." fo:content-width="1.4in" src="/files/ftp_upload/52869/52869eq4.JPG" width="200" data-altupdatedat="1787630408000" data-alt="Equation 4">
<ol start="6">
	<li>Gold plate the probes contact points (4 contacts) on the 2 x 2 x 10 mm3 piece cut from the sample to alleviate the contact resistance issues.
	<ol>
		<li>In order to sputter gold only on the desired contact areas, wrap a scotch-tape around the 2 x 2 x 10 mm3 sample to use as a stencil. Leave the 2 x 2 mm2 faces un-covered. Using a razor blade, cut out 2 very small holes (approximately 1 mm in diameter) in the middle of the 2 x 10 mm2 face along a line separated by the probes distance.</li>
		<li>Sputter a ~ 200 nm-thick gold film using a bench-top gold sputtering unit.21</li>
	</ol>
	</li>
	<li>Measure the electrical transport properties, namely the electrical conductivity and Seebeck coefficient) of the sample as a function of temperature22,23.
	<ol>
		<li>Measure electrical conductivity using the four-terminal method. Measure the Seebeck coefficient on the same setup using the measurements of temperature and voltage via the two middle thermocouple “probes”. Measure the distance between these two probes using a digital microscope. More details on the electrical transport measurements can be found elsewhere.22,23</li>
	</ol>
	</li>
	<li>Measure the Hall carrier concentration as a function of temperature on the 8 x 5 x 1 mm3 sample using a Physical Properties Measurement System.24</li>
</ol>

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<li>Kovalevsky, A. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Towards+a+High+Thermoelectric+Performance+in+Rare-Earth+Substituted+SrTiO3%3A+Effects+Provided+by+Strongly-Reducing+Sintering+Conditions%5BTitle%5D)+AND+%22Phys.+Chem%22%5BJournal%5D)">Towards a High Thermoelectric Performance in Rare-Earth Substituted SrTiO3: Effects Provided by Strongly-Reducing Sintering Conditions.</a> Phys. Chem. 16, 26946(2014).</li>
<li>Dawson, J. A., Tanaka, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Local+Structure+and+Energetics+of+Pr-+and+La-Doped+SrTiO3+Grain+Boundaries+and+the+Influence+on+Core%E2%80%93Shell+Structure+Formation%5BTitle%5D)+AND+%22J.+Phys.+Chem.+C%22%5BJournal%5D)">Local Structure and Energetics of Pr- and La-Doped SrTiO3 Grain Boundaries and the Influence on Core–Shell Structure Formation.</a> J. Phys. Chem. C. 118, 25765-25778 (2014).</li>
<li>Mehdizadeh Dehkordi, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((New+Insights+on+the+Synthesis+and+Electronic+Transport+in+Bulk+Polycrystalline+Pr-doped+SrTiO3%E2%88%92%CE%B4%5BTitle%5D)+AND+%22Appl.+Phys.+Lett%22%5BJournal%5D)">New Insights on the Synthesis and Electronic Transport in Bulk Polycrystalline Pr-doped SrTiO3−δ.</a> Appl. Phys. Lett. 117, 055102(2015).</li>
</ol>

The authors have nothing to disclose.

In this protocol, we have presented the steps of the synthesis strategy in order to successfully prepare bulk polycrystalline Pr-doped SrTiO3 ceramics exhibiting improved electronic and thermoelectric properties. The main steps of the protocol include (i) the solid-state synthesis of the doped SrTiO3 powder in air under atmospheric pressure and (ii) taking advantage of the capabilities of spark plasma sintering technique to densify the as-prepared powder into high-density bulk ceramics and at the sa...

Oxide thermoelectrics were shown to be promising candidates for high-temperature thermoelectric applications, from stability and cost perspectives to electronic transport properties. Among the n-type oxide thermoelectrics, highly doped strontium titanate (STO) has attracted much attention due to its intriguing electronic properties. However, a large total thermal conductivity (&#954; ~ 12 W m-1 K-1 at 300 K for single crystals)1 and a low carrier mobility (&#181; ~ 6 cm2 V-1 sec-1 at 300 K for single crystals)1 detrimentally affect the thermoelectric performance which is evaluated by a dimensionless figure of merit, ZT = &#945;2&#963;T/&#954;, where &#945; is the Seebeck coefficient, &#963; the electrical conductivity, T the absolute temperature in Kelvin, and &#954; the total thermal conductivity. We herein define the numerator as the power factor, PF = &#945;2&#963;T. In order for this oxide thermoelectric material to compete with other high-temperature thermoelectrics (such as SiGe alloys), a more pronounced increase in the power factor and/or decrease in lattice thermal conductivity are required.
The majority of the experimental studies in order to improve the thermoelectric properties of STO have mainly focused on the reduction of thermal conductivity through strain-field and mass fluctuation scattering of phonons. These attempts include: (i) Single- or double-doping of the Sr2+ and/or Ti4+ sites, as the main efforts with respect to this direction,2,3 (ii) Synthesis of natural superlattice Ruddlesden&#8211;Popper structures in order to further reduce the thermal conductivity through insulating SrO layers,4 and (iii) Composite engineering by addition of a nanosized second phase.5 However, up until recently, no enhancement strategy has been reported to substantially increase the thermoelectric power factor in these oxides. The reported maximum power factor (PF) values in bulk single- and poly-crystalline STO have been confined to an upper limit of PF &#60; 1.0 W m-1 K-1.
A variety of synthesis approaches and processing techniques have been employed to implement the ideas attempted above. The powder synthesis routes include conventional solid-state reaction,6 sol-gel,7 hydrothermal,8 and combustion synthesis,9 whereas conventional sintering,6 hot pressing10 and recently spark plasma sintering12 are among the common techniques used to densify the powders into bulk ceramics. However, for a similar dopant (e.g., La) and doping concentration, the resulting bulk ceramics exhibit a range of electronic and thermal transport properties. This is in large due to the strongly process-dependent defect chemistry of SrTiO3 which results in synthesis-dependent properties. There is only a handful of reports optimizing the synthesis and processing parameters to benefit thermoelectric transport. It is worth mentioning that due to the very small phonon mean free path in SrTiO3 (lph~2 nm at 300 K),11 nanostructuring is not a viable option for the improvement of the TE performance of bulk STO ceramics primarily through the reduction of the lattice thermal conductivity.
Recently, we reported more than 30% improvement in the thermoelectric figure of merit in non-uniformly Pr-doped SrTiO3 ceramics originating from a simultaneously enhanced thermoelectric power factor and reduced thermal conductivity.12,13 In this detailed video protocol, we present and discuss the steps of our synthesis strategy for the preparation of these Pr-doped STO ceramics exhibiting improved electronic and thermoelectric properties.

<table><tbody><tr><td>SrCO&lt;sub&gt;3&lt;/sub&gt; Powder, 99.9%</td><td>Sigma Aldrich</td><td>472018</td><td></td></tr><tr><td>TiO&lt;sub&gt;2&lt;/sub&gt; Nanopowder, 99.5%</td><td>Sigma Aldrich</td><td>718467</td><td></td></tr><tr><td>Pr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Sintered Lumps, 99.9%</td><td>Alfa Aesar</td><td>35663&amp;nbsp;</td><td></td></tr><tr><td>Spark Plasma Sintering&amp;nbsp;</td><td>Dr. Sinter Lab</td><td>SPS-515S</td><td></td></tr><tr><td>Resistivity/Seebeck Coefficient Measurement System</td><td>Ulvac-Riko</td><td>ZEM-2</td><td></td></tr><tr><td>Laser Flash Thermal Diffusivity Measurement System</td><td>Netzsch</td><td>LFA-457 Microflash</td><td></td></tr><tr><td>Differential Scanning Calorimetry (DSC) System</td><td>Netzsch</td><td>404C Pegasus</td><td></td></tr><tr><td>Physical Property Measurement system (PPMS)</td><td>Quantum Design</td><td></td><td></td></tr><tr><td>Field Emission Scanning Electron Microscope (FE-SEM)</td><td>Hitachi</td><td>SU-6600</td><td></td></tr><tr><td>Energyy-dispersive X-ray Spectroscopy (EDS)</td><td>Oxford Instruments</td><td></td><td></td></tr><tr><td>X-ray Diffractometer</td><td>Rigaku</td><td>Ultima IV</td><td></td></tr><tr><td>Bench-top Sputter Coater</td><td>Denton Vacuum</td><td>Desk II</td><td></td></tr><tr><td>Diamond&amp;nbsp; Wheel Saw</td><td>South Bay Technology</td><td></td><td></td></tr></tbody></table>

synthesis of non-uniformly pr-doped srtio3 ceramics and their thermoelectric properties

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

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

X-ray diffractions patterns were collected for the as-prepared powders and the corresponding bulk ceramics as a function of Pr-content (Figure 1) in order to study the effect of Pr-doping on the SrTiO3 lattice, solubility of Pr in SrTiO3 and the formation of secondary phase(s). The patterns confirm the formation of SrTiO3 phase in all the as-prepared powders where the reflections can be indexed to a cubic lattice with space group (Figure 1A). The monotoni...

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

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.

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Research

JoVE Journal

Chemistry

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

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Learn to synthesize Pr-doped SrTiO3 ceramics using solid-state reaction and spark plasma sintering for enhanced thermoelectric performance. This method improves carrier mobility and reduces thermal conductivity significantly.

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

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