Giacomo Cerretti | Jet Propulsion Laboratory, California Institute of Technology (original) (raw)
Papers by Giacomo Cerretti
Chemistry of Materials, Oct 11, 2021
Chemistry of Materials, Oct 27, 2020
Yb 14 MnSb 11 is a p-type high-temperature thermoelectric material with operational temperatures ... more Yb 14 MnSb 11 is a p-type high-temperature thermoelectric material with operational temperatures as high as 1273 K. Rare-earth (RE) substitution into this phase has been shown to increase the melting point further while also decreasing the sublimation rate. Solid solutions of 3+ RE elements with Yb 2+ in Yb 14 MnSb 11 have shown to have increased stability against oxidation. Ce is an abundant RE element, and the substitution of Ce 3+ on the Yb 2+ sites should increase the thermoelectric efficiency of the material due to a decrease in carrier concentration. Samples of Yb 14−x Ce x MnSb 11 (x ∼ 0.4) were synthesized using ball milling, followed by annealing and consolidation via spark plasma sintering. The systematic addition of a small increase of excess Mn and the resulting compositions were investigated. Small amounts of impurities in the samples, such as Yb 2 O 3 and Mn, are correlated with negative attributes in the resistivity data. Hall effect measurements revealed a reduced carrier concentration of ∼44% at 600 K over Yb 14 MnSb 11 , and adjusting the stoichiometry toward Yb 13.6 Ce 0.4 MnSb 11 leads to increases in resistivity and the Seebeck coefficient with a reduction in thermal conductivity. Yb 13.6 Ce 0.4 MnSb 11 shows an improved average zT avg = 0.80 when compared to Yb 14 MnSb 11 (0.71) and no degradation when exposed to ambient air for 77 days at room temperature. Thermogravimetric analysis of air oxidation shows that Yb 13.6 Ce 0.4 MnSb 11 and Yb 14 MnSb 11 do not oxidize until 700 K.
Journal of Applied Physics, 2019
Many of the missions proposed and successfully completed by the National Aeronautics and Space Ad... more Many of the missions proposed and successfully completed by the National Aeronautics and Space Administration seek to scientifically investigate remote locations in our solar system, in particular to better understand the origin, evolution and structure of planetary systems. Long-lived, robust power systems are a fundamental capability for such missions, and radioisotope thermoelectric generators (RTGs) have proven to be a reliable power for exploration missions in deep space for the past 50 years. With increasing power needs for future missions, the improvement of thermoelectric materials’ conversion efficiency is necessary. In this paper, we show how compositing with inert metallic inclusions can be efficiently used to improve the electronic properties of Yb14MnSb11. In this study, we found that the power factor of the p-type high temperature material, Yb14MnSb11, increases from ∼8 to ∼11.5 μW cm−1 K−2 when composited with 5 vol. % W particles. At the same time, the composite samp...
physica status solidi (a), 2008
Applied Thermal Engineering, 2021
Energy savings motivated by economic and environmental reasons have brought attention to waste he... more Energy savings motivated by economic and environmental reasons have brought attention to waste heat recovery technologies. Thermoelectric generators, previously employed as electric power generators in harsh conditions such as the found in space missions and remote ground locations, have arisen as an option to recover waste energy. Thermoelectric generators convert heat into electric power, but the low conversion efficiency of thermoelectric materials involves a challenge in the integration of thermoelectric generators to heat sources, as more energy losses than savings can be caused. As a result, the design process must be tailored to the system from which energy is to be recovered. This work fills the gap in previous reviewed literature, providing considerations focused on thermal management of heat sources for the design of thermoelectric generators and methods to evaluate specific energy sources and prototypes are presented. In addition, several applications were reviewed and main opportunities, advantages and drawbacks in different sectors are presented.
Science Advances
Yb 14 MnSb 11 and Yb 14 MgSb 11 are among the best p-type high-temperature (>1200 K) thermoele... more Yb 14 MnSb 11 and Yb 14 MgSb 11 are among the best p-type high-temperature (>1200 K) thermoelectric materials, yet other compounds of this Ca 14 AlSb 11 structure type have not matched their stability and efficiency. First-principles computations show that the features in the electronic structures that have been identified to lead to high thermoelectric performances are present in Yb 14 ZnSb 11 , which has been presumed to be a poor thermoelectric material. We show that the previously reported low power factor of Yb 14 ZnSb 11 is not intrinsic and is due to the presence of a Yb 9 Zn 4+ x Sb 9 impurity uniquely present in the Zn system. Phase-pure Yb 14 ZnSb 11 synthesized through a route avoiding the impurity formation reveals its exceptional high-temperature thermoelectric properties, reaching a peak zT of 1.2 at 1175 K. Beyond Yb 14 ZnSb 11 , the favorable band structure features for thermoelectric performance are universal among the Ca 14 AlSb 11 structure type, opening the po...
Materials Science and Engineering: R: Reports, 2018
Thermoelectricity offers a sustainable path to recover and convert waste heat into readily availa... more Thermoelectricity offers a sustainable path to recover and convert waste heat into readily available electric energy, and has been studied for more than two centuries. From the controversy between Galvani and Volta on the Animal Electricity, dating back to the end of the XVIII century and anticipating Seebeck's observations, the understanding of the physical mechanisms evolved along
Inorganic chemistry, Jan 5, 2018
The Magnéli phase VO was synthesized in gram amounts from a powder mixture of VO/VO and vanadium ... more The Magnéli phase VO was synthesized in gram amounts from a powder mixture of VO/VO and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magnéli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared VO has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K) while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (μΩ m), a Seebeck coefficient of α = -(35 ± 2) μV K, which leads to a power factor of PF = 4.9 ± 0.8 × 10W (m K) at ∼600 K. Advances in the application of Magnéli phases are mostly hindered by synthetic and processing challenges, especially when metastable and nanostructured materials such as VO are involved. This study gives insight into the complicat...
J. Mater. Chem. A, 2017
Engineering of nanoscaled structures allows to control the electrical and thermal transport in so... more Engineering of nanoscaled structures allows to control the electrical and thermal transport in solids for thermoelectric applications where a combination of low thermal conductivity and low electrical resistivity is required.
Polymer, 2017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Laser 3D Manufacturing III, 2016
Liquid Crystalline Elastomers (LCEs) are very promising smart materials that can be made sensitiv... more Liquid Crystalline Elastomers (LCEs) are very promising smart materials that can be made sensitive to different external stimuli, such as heat, pH, humidity and light, by changing their chemical composition. In this paper we report the implementation of a nematically aligned LCE actuator able to undergo large light-induced deformations. We prove that this property is still present even when the actuator is submerged in fresh water. Thanks to the presence of azo-dye moieties, capable of going through a reversible trans-cis photo-isomerization, and by applying light with two different wavelengths we managed to control the bending of such actuator in the liquid environment. The reported results represent the first step towards swimming microdevices powered by light.
physica status solidi (a), 2016
Thermoelectric devices can help to tackle future challenges in the energy sector through the conv... more Thermoelectric devices can help to tackle future challenges in the energy sector through the conversion of waste heat directly into usable electric energy. For a wide applicability low-cost materials with reasonable thermoelectric performances and cost-efficient preparation techniques are required. In this context metal oxides are an interesting class of materials because of their inherent hightemperature stability and relative high sustainability. Their thermoelectric performance, however, needs to be improved for wide application. Compounds with adaptive structures are a very interesting class of materials. A slight reduction of earlytransition metal oxides generates electrons as charge carriers and crystallographic shear planes as structure motif. The crystallographic shear planes lead to a reduction of intrinsic thermal conductivity. At the same time, the electronic transport properties canbetunedbythedegreeofreduction.Sofaronlyafewtransition metal oxides with adaptive structures have been investigated with respect to their thermoelectric properties, leaving much room for improvement. This review gives an overview of thermoelectric oxides, highlights the structural aspects of the crystallographic shear planes and the resulting thermoelectric properties.
Materials Horizons, 2015
Tetragonal tungsten bronzes Nb8−xW9+xO47−δallow a continuous variation of the charge carrier conc... more Tetragonal tungsten bronzes Nb8−xW9+xO47−δallow a continuous variation of the charge carrier concentration while fulfilling the concept of a “phonon-glass electron-crystal” through intrinsic nanostructure.
Journal of Solid State Chemistry, 2018
Yb14MnSb11 is a member of a remarkable structural family of compounds that are classified accordi... more Yb14MnSb11 is a member of a remarkable structural family of compounds that are classified according to the concept of Zintl. This structure type, of which the prototype is Ca14AlSb11, provides a flexible framework for tuning structure-property relationships and hence the physical and chemical properties of compounds. Compounds within this family show exceptional high temperature thermoelectric performance at temperatures above 300 K and unique magnetic and transport behavior at temperatures below 300 K. This review provides an overview of the structure variants, the magnetic properties, and the thermoelectric properties. Suggestions for directions of future research are provided. One active research area is to systematically explore more complex compositions such as Ca11Sb10, K4Pb9, Na8Si46, Ca14AlSb11 and KBa2InAs3. 3-7 The other direction is to replace the alkaline earth metals with divalent rare earth elements (Sm, Eu and Yb) along with the introduction of transition metals into structures, typically replacing the less electronegative metalloid in the anionic framework. 8-10 Combinations of these two directions led to compounds such as Yb14MnSb11, Pr4MnSb9, Eu10Mn6Sb13, Yb9Zn4+xBi9 and Cs13Nb2In6As10. 11-16 The complexity of compositions can be combined with a small flexibility in electron counting. For example, Yb14MnSb11 and Yb9Zn4+xBi9 do not strictly follow the Zintl-Klemm concept. Yb14MnSb11 has Mn 2+ instead of a group 13 element such as in Ca14AlSb11 and therefore is electron deficient, 17 and Yb9Zn4+xSb9 has interstitial Zn atoms which can be compositionally varied to achieve specific properties. 18 At the same time, the total number of valence electrons within an identical Zintl phase structure type with different elements may also vary slightly but the variance can be quite small and limited for many structure types that can be described by the Zintl concept. Therefore, with the introduction of transition elements, new electronic properties are possible, but complete transfer of electrons and clear counting of valence electrons remains a criterion for describing transition and rare earth metal containing Zintl phase compounds. Binary Zintl phase compounds which have compositions of simple ratios of elements usually adopt the structures of known oxides or halides, in which anions and cations are isolated in the structure with no covalent bonding. 2, 19 Both isolated anions, polyanions or clusters in Zintl phase compounds can provide complex compositions such as those represented by Ca11Sb10 and K4Pb9. 3, 4 Polyanions or clusters are formed to compensate for lack of enough electrons from the electropositive element to satisfy valence to form a simple one atom anion. Sb forms Sb-Sb single bonds in the Ca11Sb10 structure type resulting in Sb2 4and Sb4 2polyanions in the structure. 3 The Zintl electron counting provides the following charge balanced scenario: 11Ca 2+ + 4Sb 3-+ 2Sb2 4-+ Sb4 2-. Two types of clusters exist in K4Pb9 with the same formal oxidation state: a monocapped square antiprism and a tricapped trigonal prism of Pb9 4-. 4 The Zintl electron counting works for double the formula, K8Pb9, providing 8K + + 2Pb9 4-. The polyanions or clusters can combine from infinite units or a framework structure. For example, anionic clathrates such as Na8Si46 have an infinite framework of silicon with sodium filling the cages. 5 Ternary and quaternary Zintl phases can have even more complex structures. KBa2InAs3 has both [In2As7] 13isolated clusters and one dimensional infinite chains of [In2As5] 7-. 7 All the alkali and alkali earth metals are isolated as electron donors with no covalent bonding to the anions. The introduction of rare earth elements
Chemistry of Materials, Oct 11, 2021
Chemistry of Materials, Oct 27, 2020
Yb 14 MnSb 11 is a p-type high-temperature thermoelectric material with operational temperatures ... more Yb 14 MnSb 11 is a p-type high-temperature thermoelectric material with operational temperatures as high as 1273 K. Rare-earth (RE) substitution into this phase has been shown to increase the melting point further while also decreasing the sublimation rate. Solid solutions of 3+ RE elements with Yb 2+ in Yb 14 MnSb 11 have shown to have increased stability against oxidation. Ce is an abundant RE element, and the substitution of Ce 3+ on the Yb 2+ sites should increase the thermoelectric efficiency of the material due to a decrease in carrier concentration. Samples of Yb 14−x Ce x MnSb 11 (x ∼ 0.4) were synthesized using ball milling, followed by annealing and consolidation via spark plasma sintering. The systematic addition of a small increase of excess Mn and the resulting compositions were investigated. Small amounts of impurities in the samples, such as Yb 2 O 3 and Mn, are correlated with negative attributes in the resistivity data. Hall effect measurements revealed a reduced carrier concentration of ∼44% at 600 K over Yb 14 MnSb 11 , and adjusting the stoichiometry toward Yb 13.6 Ce 0.4 MnSb 11 leads to increases in resistivity and the Seebeck coefficient with a reduction in thermal conductivity. Yb 13.6 Ce 0.4 MnSb 11 shows an improved average zT avg = 0.80 when compared to Yb 14 MnSb 11 (0.71) and no degradation when exposed to ambient air for 77 days at room temperature. Thermogravimetric analysis of air oxidation shows that Yb 13.6 Ce 0.4 MnSb 11 and Yb 14 MnSb 11 do not oxidize until 700 K.
Journal of Applied Physics, 2019
Many of the missions proposed and successfully completed by the National Aeronautics and Space Ad... more Many of the missions proposed and successfully completed by the National Aeronautics and Space Administration seek to scientifically investigate remote locations in our solar system, in particular to better understand the origin, evolution and structure of planetary systems. Long-lived, robust power systems are a fundamental capability for such missions, and radioisotope thermoelectric generators (RTGs) have proven to be a reliable power for exploration missions in deep space for the past 50 years. With increasing power needs for future missions, the improvement of thermoelectric materials’ conversion efficiency is necessary. In this paper, we show how compositing with inert metallic inclusions can be efficiently used to improve the electronic properties of Yb14MnSb11. In this study, we found that the power factor of the p-type high temperature material, Yb14MnSb11, increases from ∼8 to ∼11.5 μW cm−1 K−2 when composited with 5 vol. % W particles. At the same time, the composite samp...
physica status solidi (a), 2008
Applied Thermal Engineering, 2021
Energy savings motivated by economic and environmental reasons have brought attention to waste he... more Energy savings motivated by economic and environmental reasons have brought attention to waste heat recovery technologies. Thermoelectric generators, previously employed as electric power generators in harsh conditions such as the found in space missions and remote ground locations, have arisen as an option to recover waste energy. Thermoelectric generators convert heat into electric power, but the low conversion efficiency of thermoelectric materials involves a challenge in the integration of thermoelectric generators to heat sources, as more energy losses than savings can be caused. As a result, the design process must be tailored to the system from which energy is to be recovered. This work fills the gap in previous reviewed literature, providing considerations focused on thermal management of heat sources for the design of thermoelectric generators and methods to evaluate specific energy sources and prototypes are presented. In addition, several applications were reviewed and main opportunities, advantages and drawbacks in different sectors are presented.
Science Advances
Yb 14 MnSb 11 and Yb 14 MgSb 11 are among the best p-type high-temperature (>1200 K) thermoele... more Yb 14 MnSb 11 and Yb 14 MgSb 11 are among the best p-type high-temperature (>1200 K) thermoelectric materials, yet other compounds of this Ca 14 AlSb 11 structure type have not matched their stability and efficiency. First-principles computations show that the features in the electronic structures that have been identified to lead to high thermoelectric performances are present in Yb 14 ZnSb 11 , which has been presumed to be a poor thermoelectric material. We show that the previously reported low power factor of Yb 14 ZnSb 11 is not intrinsic and is due to the presence of a Yb 9 Zn 4+ x Sb 9 impurity uniquely present in the Zn system. Phase-pure Yb 14 ZnSb 11 synthesized through a route avoiding the impurity formation reveals its exceptional high-temperature thermoelectric properties, reaching a peak zT of 1.2 at 1175 K. Beyond Yb 14 ZnSb 11 , the favorable band structure features for thermoelectric performance are universal among the Ca 14 AlSb 11 structure type, opening the po...
Materials Science and Engineering: R: Reports, 2018
Thermoelectricity offers a sustainable path to recover and convert waste heat into readily availa... more Thermoelectricity offers a sustainable path to recover and convert waste heat into readily available electric energy, and has been studied for more than two centuries. From the controversy between Galvani and Volta on the Animal Electricity, dating back to the end of the XVIII century and anticipating Seebeck's observations, the understanding of the physical mechanisms evolved along
Inorganic chemistry, Jan 5, 2018
The Magnéli phase VO was synthesized in gram amounts from a powder mixture of VO/VO and vanadium ... more The Magnéli phase VO was synthesized in gram amounts from a powder mixture of VO/VO and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magnéli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared VO has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K) while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (μΩ m), a Seebeck coefficient of α = -(35 ± 2) μV K, which leads to a power factor of PF = 4.9 ± 0.8 × 10W (m K) at ∼600 K. Advances in the application of Magnéli phases are mostly hindered by synthetic and processing challenges, especially when metastable and nanostructured materials such as VO are involved. This study gives insight into the complicat...
J. Mater. Chem. A, 2017
Engineering of nanoscaled structures allows to control the electrical and thermal transport in so... more Engineering of nanoscaled structures allows to control the electrical and thermal transport in solids for thermoelectric applications where a combination of low thermal conductivity and low electrical resistivity is required.
Polymer, 2017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Laser 3D Manufacturing III, 2016
Liquid Crystalline Elastomers (LCEs) are very promising smart materials that can be made sensitiv... more Liquid Crystalline Elastomers (LCEs) are very promising smart materials that can be made sensitive to different external stimuli, such as heat, pH, humidity and light, by changing their chemical composition. In this paper we report the implementation of a nematically aligned LCE actuator able to undergo large light-induced deformations. We prove that this property is still present even when the actuator is submerged in fresh water. Thanks to the presence of azo-dye moieties, capable of going through a reversible trans-cis photo-isomerization, and by applying light with two different wavelengths we managed to control the bending of such actuator in the liquid environment. The reported results represent the first step towards swimming microdevices powered by light.
physica status solidi (a), 2016
Thermoelectric devices can help to tackle future challenges in the energy sector through the conv... more Thermoelectric devices can help to tackle future challenges in the energy sector through the conversion of waste heat directly into usable electric energy. For a wide applicability low-cost materials with reasonable thermoelectric performances and cost-efficient preparation techniques are required. In this context metal oxides are an interesting class of materials because of their inherent hightemperature stability and relative high sustainability. Their thermoelectric performance, however, needs to be improved for wide application. Compounds with adaptive structures are a very interesting class of materials. A slight reduction of earlytransition metal oxides generates electrons as charge carriers and crystallographic shear planes as structure motif. The crystallographic shear planes lead to a reduction of intrinsic thermal conductivity. At the same time, the electronic transport properties canbetunedbythedegreeofreduction.Sofaronlyafewtransition metal oxides with adaptive structures have been investigated with respect to their thermoelectric properties, leaving much room for improvement. This review gives an overview of thermoelectric oxides, highlights the structural aspects of the crystallographic shear planes and the resulting thermoelectric properties.
Materials Horizons, 2015
Tetragonal tungsten bronzes Nb8−xW9+xO47−δallow a continuous variation of the charge carrier conc... more Tetragonal tungsten bronzes Nb8−xW9+xO47−δallow a continuous variation of the charge carrier concentration while fulfilling the concept of a “phonon-glass electron-crystal” through intrinsic nanostructure.
Journal of Solid State Chemistry, 2018
Yb14MnSb11 is a member of a remarkable structural family of compounds that are classified accordi... more Yb14MnSb11 is a member of a remarkable structural family of compounds that are classified according to the concept of Zintl. This structure type, of which the prototype is Ca14AlSb11, provides a flexible framework for tuning structure-property relationships and hence the physical and chemical properties of compounds. Compounds within this family show exceptional high temperature thermoelectric performance at temperatures above 300 K and unique magnetic and transport behavior at temperatures below 300 K. This review provides an overview of the structure variants, the magnetic properties, and the thermoelectric properties. Suggestions for directions of future research are provided. One active research area is to systematically explore more complex compositions such as Ca11Sb10, K4Pb9, Na8Si46, Ca14AlSb11 and KBa2InAs3. 3-7 The other direction is to replace the alkaline earth metals with divalent rare earth elements (Sm, Eu and Yb) along with the introduction of transition metals into structures, typically replacing the less electronegative metalloid in the anionic framework. 8-10 Combinations of these two directions led to compounds such as Yb14MnSb11, Pr4MnSb9, Eu10Mn6Sb13, Yb9Zn4+xBi9 and Cs13Nb2In6As10. 11-16 The complexity of compositions can be combined with a small flexibility in electron counting. For example, Yb14MnSb11 and Yb9Zn4+xBi9 do not strictly follow the Zintl-Klemm concept. Yb14MnSb11 has Mn 2+ instead of a group 13 element such as in Ca14AlSb11 and therefore is electron deficient, 17 and Yb9Zn4+xSb9 has interstitial Zn atoms which can be compositionally varied to achieve specific properties. 18 At the same time, the total number of valence electrons within an identical Zintl phase structure type with different elements may also vary slightly but the variance can be quite small and limited for many structure types that can be described by the Zintl concept. Therefore, with the introduction of transition elements, new electronic properties are possible, but complete transfer of electrons and clear counting of valence electrons remains a criterion for describing transition and rare earth metal containing Zintl phase compounds. Binary Zintl phase compounds which have compositions of simple ratios of elements usually adopt the structures of known oxides or halides, in which anions and cations are isolated in the structure with no covalent bonding. 2, 19 Both isolated anions, polyanions or clusters in Zintl phase compounds can provide complex compositions such as those represented by Ca11Sb10 and K4Pb9. 3, 4 Polyanions or clusters are formed to compensate for lack of enough electrons from the electropositive element to satisfy valence to form a simple one atom anion. Sb forms Sb-Sb single bonds in the Ca11Sb10 structure type resulting in Sb2 4and Sb4 2polyanions in the structure. 3 The Zintl electron counting provides the following charge balanced scenario: 11Ca 2+ + 4Sb 3-+ 2Sb2 4-+ Sb4 2-. Two types of clusters exist in K4Pb9 with the same formal oxidation state: a monocapped square antiprism and a tricapped trigonal prism of Pb9 4-. 4 The Zintl electron counting works for double the formula, K8Pb9, providing 8K + + 2Pb9 4-. The polyanions or clusters can combine from infinite units or a framework structure. For example, anionic clathrates such as Na8Si46 have an infinite framework of silicon with sodium filling the cages. 5 Ternary and quaternary Zintl phases can have even more complex structures. KBa2InAs3 has both [In2As7] 13isolated clusters and one dimensional infinite chains of [In2As5] 7-. 7 All the alkali and alkali earth metals are isolated as electron donors with no covalent bonding to the anions. The introduction of rare earth elements