Depuis les cinquante dernières années, les préoccupations d’ordre énergétique sont au cœur de l’actualité. Or, une grande partie de l’énergie produite est rejetée et perdue sous forme de chaleur. Ainsi, la récupération d’énergie par des générateurs thermoélectriques apparaît comme une solution pour le mixe énergétique de demain.La thermoélectricité est la conversion directe et réciproque entre énergie thermique et électrique. Les générateurs thermoélectriques sont constitués d’un assemblage de plots de semi-conducteurs de type n et p. Un gradient de température appliqué entre les deux faces du générateur entraîne une migration des charges du matériau qui génère un courant électrique.Les systèmes thermoélectriques ont attiré l’attention du monde scientifique grâce à leurs avantages comparativement aux moyens de récupération d’énergie plus conventionnels. Ce sont des dispositifs compacts, statiques, silencieux et fiables, qui possèdent une longue durée de vie sans nécessiter de maintenance et impactant peu l’environnement.Pour la récupération d'énergie, le challenge actuel est la perte d’énergie thermique des automobiles et des camions ainsi que la chaleur perdue générée dans les industries de la métallurgie ou du nucléaire, par exemple. Ces deux segments nécessitent l’utilisation de modules thermoélectriques ayant un rendement optimum dans la gamme de température 300-600 °C.La performance d’un matériau thermoélectrique est exprimée par le facteur de mérite ZT, donné par l’expression : ZT=S2σT/к. Un ZT élevé peut être obtenu en optimisant les propriétés de transport du matériau. Le coefficient de Seebeck (S), et la conductivité électrique (σ), doivent être le plus élevé possible, alors que la conductivité thermique (κ) doit rester faible.Afin d’être viable pour une production industrielle, un matériau thermoélectrique doit répondre à un certain nombre de critères. Premièrement, ses composants doivent être non toxiques, peu chers et abondants. Ensuite, la voie de fabrication doit être robuste et compatible avec une production en grand volume. Enfin, les matériaux élaborés doivent posséder des propriétés thermoélectriques satisfaisantes dans la gamme de température de l’application visée. Ils doivent également être stables selon les environnements liés à l’application et avoir une bonne tenue mécanique.Les matériaux de type half-Heusler apparaissent comme prometteurs pour la génération de puissance thermoélectrique dans la gamme de température 300-600 °C. En effet, ils possèdent un coefficient de Seebeck et une conductivité électrique élevés. Cependant, leur conductivité thermique est relativement haute comparée aux autres matériaux thermoélectriques.Ce travail de thèse s’est donc focalisé sur l’étude des relations microstructure-propriétés thermoélectriques de matériaux half-Heusler de composition générique (Hf,Zr,Ti)Ni(Sb,Sn) et (Hf,Zr,Ti)Co(Sb,Sn) et de leurs possibles variantes. Les compositions testées ont toutes été synthétisées de la même manière : une fusion par induction permet d’obtenir des lingots qui sont ensuite réduits en poudre par broyage, celle-ci est ensuite frittée par frittage SPS (spark plasma sintering) afin d’obtenir une pastille dense et polycristalline. Les propriétés thermoélectriques et la microstructure de ces échantillons sont ensuite caractérisées et discutées.Un des objectifs de ce travail de thèse était également de réduire coût au kilogramme de ces matériaux half-Heusler, sans impacter de manière négative leurs propriétés thermoélectriques. Nous y sommes parvenus, d’une part, en réduisant la concentration en hafnium incorporé dans les formulations, et d’autre part, en simplifiant le processus de fabrication. En effet, nous avons observé qu’une synthèse sous air des poudres half-Heusler permettait la formation in-situ de précipités d’oxydes, agissant comme source de diffusion des phonons et donc favorisant la diminution de la conductivité thermique. / The search for alternative energy technologies has taken an accelerated pace in the last 50 years due to an increasing concern about climate change. In this quest to find new energy sources, it is interesting to point out that a lot of energy is wasted as heat released into the environment. As a potential solution, thermoelectric power generators could be used to transform the waste heat into useful electrical energy.Thermoelectric generators are converting directly heat into electricity and vice versa. They consist in an assembly of n and p-type semiconducting legs connected electrically in series and thermally in parallel. An applied temperature difference between n and p-sides drives charge carriers displacement in the material from the hot side to the cold one. Therefore a current flow is generated through the circuit. Thermoelectric devices have attracted interest because of their advantages over conventional power generator: no moving part, no liquid involved, reliability, noiseless, long life time without maintenance and also low environmental impact.Over the last several decades, the increased energy demand combined to the environmental concerns, leads to another potential use of thermoelectricity as an alternative energy source by recovering the huge amount of heat lost in industrial or domestic applications. Presently, wasted-heat recovery in cars and trucks and wasted-heat in industry (metallurgy/nuclear…) are becoming a major concern. Both recovery problematics may be addressed using thermoelectric devices efficient in the 300-500 °C temperature range.Numerous thermoelectric materials couples have been investigated and developed over the last 20 years. Most of the already known class of thermoelectric materials have been improved and new classes have been developed, leading to a significant improvement of ZT values being optimum in different temperature ranges. In order to be efficient and to be viable for large scale manufacturing of power generators, a thermoelectric material has to fulfill several requirements. First, the raw materials chosen have to be non-toxic, cheap and abundant. Secondly, the manufacturing process should be robust and compatible to the production of a high volume of materials per day. Last but not least, the elaborated materials have to exhibit acceptable thermoelectric properties in the temperature range of interest for the final application. They must also have a long-term thermal stability in different kinds of environments and good mechanical properties.Half-Heusler materials have been shown to be good candidates in the 300 to 600 °C temperature range. Indeed, due to their semiconductor like band structure, they exhibit a large Seebeck coefficient and high electrical conductivity. Unfortunately, half-Heusler’s thermal conductivity is rather high when compared to other thermoelectric materials. Therefore, the main research efforts on half-Heusler formulations, devoted to be used for thermoelectric applications, have been focused on decreasing the thermal conductivity, while keeping a good electronic transport.Accordingly the main objective of the PhD thesis was to investigate the link between the microstructure and the thermoelectric properties of n and p-type half-Heusler alloys from the generic compositions MNiSn (n-type) and MCoSb (p-type), with M being Ti, Zr and Hf. All investigated compositions have been elaborated by a three step process: (i) ingots synthesis using cold crucible levitation melting, (ii) subsequent ball milling to obtain a calibrated powder and (iii) sintering by spark plasma sintering to obtain dense polycrystalline pellets that are characterized regarding their microstructure and thermoelectric properties from room temperature to 500-600 °C.

Thermoelectric materials convert temperature gradients into electricity and vice-versa. These materials utilize the Seebeck effect for power generation and function without moving parts and are highly reliable. The efficiency of thermoelectric devices is related to the dimensionless figure of merit for the constituent materials, defined as where S is the Seebeck coefficient, is the electrical conductivity, is the thermal conductivity and T is the temperature. Maximizing ZT is very challenging because of interdependence of parameters, for example, increasing the electrical conductivity by increasing the carrier concentration invariably lowers S and vice versa. Presently numerous thermoelectric materials are being investigated by different research groups. Despite having high thermal conductivity, half-Heusler materials are promising candidates for thermoelectric applications due to their relatively high power factor () and the ability to tune the thermal and electrical properties through substitutional doping. 2S In this research work, I have investigated the synthesis and transport properties of half Heusler series Zr 0.5Hf0.5Ni1-xPdxSn0.99Sb0.01 (0≤x≤1). Also the role of NiO and HfO2 nanoinclusions in half –Heusler matrix were studied. The half Heusler samples were prepared by solid state reaction. Resistivity, Seebeck coefficient and thermal conductivity were measured for all samples over a temperature range from room temperature to 750K. Hall effect measurements at room temperature were also performed. Addition of NiO inclusions did result in an improvement in ZT whereas addition of 3% vol HfO2 in Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 showed 19% improvement in ZT.

High temperature waste heat recovery has been gaining attention in recent years as it forms one of the largest sources of available energy. A rapid development of thermoelectric (TE) materials that can directly convert heat into electricity through the Seebeck effect, opens promising pathway for harvesting the thermal energy from the surroundings. In order to harvest the high-quality waste heat at elevated temperature, excellent thermal and mechanical stability of the TE materials is critical for a sustainable energy harvesting. In this respect, half-Heusler (hH) alloys are one of the promising high-temperature TE materials due to their high dimensionless thermoelectric figure of merit (zT) along with excellent mechanical and thermal stability. This dissertation demonstrates novel hH compositions and microstructures for the waste heat recovery systems. Focus in the thesis is on development of high performance hH TE materials with excellent in-air thermal stability at high temperatures (>700K). This will allow manufacturing of high efficiency and durable high temperature thermoelectric generators (TEGs). In chapter 3 and 4, a comprehensive optimization of n-type MNiSn and p-type MCoSb (M = Hf, Zr, and Ti) compounds is investigated through systematic control of processing parameters during melting and sintering. The synthesis conditions were controlled to achieve the phase purity, desired microstructure and the enhanced charge-carrier transport. Optimized n-type and p-type compositions are found to exhibit zTmax ~ 1 at 773 K. Chapter 5 describes breakthrough in decoupling of TE parameters in n-type half-Heusler (hH) alloys through multi-scale nanocomposite architecture with tungsten nanoinclusions. The tungsten nanoparticles not only assist electron injection, thereby improving electrical conductivity, but also enhance the Seebeck coefficient through energy filtering effect. The microstructure comprises of disordered phases with feature sizes at multiple length scales, which assists in effective scattering of heat-carrying phonons over diverse mean-free-path ranges. Cumulatively, these effects are shown to result in outstanding thermoelectric performance of zTmax ~ 1.4 at 773 K and zTavg ~ 0.93 between 300 and 973 K. In order to deploy TE materials into a thermal energy conversion device, it is essential to understand the transformation behavior under thermal cycling at high temperatures. In-air thermal stability of the hH compositions is demonstrated in chapter 6. All the optimized compositions are found to be stable below 673 K in-air condition. The n-type MNiSn and p-type NbFeSb compounds were found to show good thermal stability even at higher temperatures (>773K), whereas MCoSb compounds did not exhibit similar level of stability. Building upon the improved material performance and thermal stability, uni-coupled TE generators are demonstrated that exhibit high power density of 13.81 W⸱cm-2 and conversion efficiency of 10.9 % under a temperature difference of 674 K. The uni-couple TEG device shows stable performance for more than 150 hours at 873 K in air. These results are very promising for deployment of TE materials in waste heat recovery systems. / Doctor of Philosophy / Based on the 2012 international energy agency (IEA) report, global waste heat energy is estimated to be in the range of 246 Exajoule (1 EJ = 10¹⁸ J). Tapping even small fraction of this wasted energy through thermal energy harvesting techniques will allow us to generate significant magnitude of green energy. Thermoelectrics (TEs) are one of the most promising thermal energy conversion materials as they offer cost-effective and environmentally friendly option with solid-state silent operation and scalability. Among many different options for high temperature TE materials, half-Heusler system is one of the leading candidates as it has the potential to provide high performance and thermal stability at temperatures as high as 873 K. The progress in developing practical half-Heusler materials has been limited for last two decades. Despite many publications, the maximum figure of merit (zT) of n-type half-Heusler materials has been stagnant (zT ~ 1.0). Further, there has been a lack of focus towards module development that can operate under realistic conditions. This dissertation provides comprehensive studies on novel thermoelectric compositions and nanocomposites that are suitable for manufacturing of high temperature modules. Microstructural architectures proposed here provide the ability to tailor electronic transport and phonon scattering beyond the commonly demonstrated regimes. Optimized materials were successfully implemented in efficient and stable thermoelectric generator exhibiting power density on the order of 13.81 W⸱cm⁻² , which is 1400 % higher than that of the fuel cell (~1 W⸱cm⁻² ).

L’amélioration de la figure de mérite ZT des matériaux thermoélectriques (TE) est actuellement entreprise via des procédés de métallurgie, tels que la nanostructuration et l’introduction contrôlée de dislocations. De tels niveaux de complexité de microstructure soulèvent la problématique du comportement mécanique associé. En effet, malgré les valeurs de dureté et module d’élasticité connues pour la plupart des matériaux TE, rares sont les données sur les mécanismes de déformation. Portant sur le Half-Heusler Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2 de type p, notre étude multi-échelle propose de caractériser les mécanismes de déformation de cet alliage. Les expérimentations menées aux échelles macroscopique, mésoscopique, et microscopique sont pensées pour déclencher puis examiner les mécanismes de plasticité. Les tests en compression sur échantillons massifs dans un environnement de pression de confinement et température ont aboutis à une rupture exclusivement fragile. Les mécanismes de rupture sont identifiés comme associés une propagation de fissure intra- et inter granulaire, dépendant de la taille de grain rencontrée par le front de fissure. La méthode « indentation toughness » à l’échelle mésoscopique permet l’insertion de fissures, où les analyses MET en front de fissure confirment une abscence d’activité de dislocations, également confirmé par 3D-EBSD. À l’échelle microscopique, les données de compression de micro-pilliers ainsi que les observations de faciès de fracture sont comparable avec les échantillons massifs. Ces résultats peuvent être utilisés comme guide pour produire des matériaux TE plus résistants à la fissuration. / Increasing the figure of merit ZT of thermoelectric (TE) alloys is a challenge that is currently attempted through various metallurgy methods, including nanostructuring and dislocation engineering. Microstructures with such level of complexity raises questions about the mechanical reliability of these new materials. Indeed, despite the values of hardness and elastic modulus known for the clear majority of TE materials, the data on deformation mechanisms are still rare. Focusing on the nanostructured p-type half-Heusler Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2, our multi-scale study aims to analyze the deformation mechanisms. Experiments conducted at macro-, meso- and micro-scale are designed to trigger and assess plasticity mechanisms. Compression testing on bulk samples subject to a confining pressure environment and temperature leads to an exclusive brittle failure. The mixed-mode failure mechanisms involve switching between intra- and inter-granular crack propagation, depending on the grain size met by the crack tip. Indentation toughness at meso-scale generates cracks, while TEM analysis of the crack tip area confirms no dislocation activity and 3D-EBSD technique confirms the mixed crack propagation behavior. At micro-scale, micro-pillar compression stress-strain curves and failure mechanisms are comparable with bulk samples testing analysis. These results can be used to provide design guidelines for more crack-resistant TE alloys.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T14:23:09Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T14:23:25Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T14:23:37Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) / Made available in DSpace on 2018-06-20T14:23:37Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) Previous issue date: 2018-05-18 / The study of the Half-Heusler alloy has drawn a lot of attention among the researchers due to their characteristics and applications, in general, to characterize as ferromagnetic alloys, constituted by non-magnetic elements. In this research, the TiNiSn alloy was produced by the Mechanical Alloyng in two routes, the first in 3h with analysis done at each hour, and the second at 4h straight. The structure and its thermal behavior were investigated by the following techniques: X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermal Treatment (TT) and Rietveld refinement. According to results obtained, respectively, it was seen that the TiNiSn alloy was produced in 4h grinding by the mechanical alloying method, its diffractograms were verified in order to discover the phases formed in the synthesized alloy in 4h, and by the analysis of differential calorimetry of scanning was seen the thermal behavior of the sample at varied temperatures in a temperature range of 30 °C and 500 °C, so it was possible to analyze the sample by the Thermal Treatment technique. / O estudo da liga Half-Heusler tem chamado muita atenção entres os pesquisadores devido as suas características e aplicações, de uma maneira geral, por caracterizarem-se como ligas ferromagnéticas, constituídas por elementos não magnéticos. Neste trabalho foi produzida e a liga TiNiSn, do tipo Half-Heusler, a fim de analisar sua estrutura. Nesta pesquisa, a liga TiNiSn foi produzida pela técnica de Moagem Mecânica de Alta Energia em dois tempos de moagem, a primeira em 3h com análise feita a cada uma hora, e a segunda em 4h sem pausas. A estrutura e seu comportamento térmico foram investigados pelas seguintes técnicas: Difração de raios X (DRX), Calorimetria Diferencial de Varredura (DSC), Tratamento Térmico (TT) e método de refinamento estrutural de Rietveld (MR). De acordo com os resultados obtidos, respectivamente, foi visto que a liga TiNiSn foi produzida em 4 h de moagem pelo método de mechanical alloying, seus difratogramas foram verificados afim de descobrir as fases formadas na liga sintetizada em 4 h, e pela análise de calorimetria diferencial de varredura (DSC) foi visto o comportamento térmico da amostra em temperaturas variadas, em uma faixa de 30 °C à 500 °C, subsequentemente, foi possível analisar a amostra pela técnica de tratamento térmico.

Il sera question dans ce mémoire de maîtrise de l’étude d’une nouvelle classification des états solides de la matière appelée isolant topologique. Plus précisément, nous étudierons cette classification chez le composé demi-Heusler GdBiPt. Nous avons principalement cherché à savoir si ce composé ternaire est un isolant topologique antiferromagnétique. Une analyse de la susceptibilité magnétique ainsi que de la chaleur spécifique du maté- riau montre la présence d’une transition antiferromagnétique à 8.85(3) K. Une mesure d’anisotropie de cette susceptibilité montre que les plans de spins sont ordonnés sui- vant la direction (1,1,1) et finalement des mesures de résistivité électronique ainsi que de l’effet Hall nous indiquent que nous avons un matériau semimétallique lorsque nous sommes en présence d’antiferromagnétisme. Présentement, les expériences menées ne nous permettent pas d’associer cet état métallique aux états surfaciques issus de l’état d’isolant topologique. / In this thesis will be discussed the study of a new way of characterizing state of matter called a topological insulator. We have mainly investigated whether the ternary compound GdBiPt, from the family of half-Heusler compounds, is an antiferromagnetic topological insulator. An analysis of the magnetic susceptibility and the specific heat of the material shows the presence of an antiferromagnetic transition at 8.85(3) K. A measurement of the anisotropy of the susceptibility shows that plan of spins are ordered according to the crystalline direction (1,1,1) and finally, measurements of electronic re- sistivity and Hall effect indicate that we have a semimetallic material when we are in the presence of antiferromagnetism. At the present, these experiments do not allow us to as- sociate this metallic state with the surface states associated with the topological insulator state of matter.

No description available.

Les matériaux thermoélectriques permettent de convertir de l'énergie thermique en énergie électrique. Leur rendement de conversion trop faible limite cependant leur utilisation à grande échelle. Plusieurs voies d'optimisation sont utilisés afin d'augmenter les rendements de conversion en diminuant la conductivité thermique. Dans cette thèse, nous modélisons les propriétés de transport thermique des matériaux half-Heusler parfaits et dopés qui présentent des propriétés thermoélectriques intéressantes. La méthode repose sur la théorie de la fonctionnelle de la densité pour calculer les propriétés harmoniques et anharmoniques des composés parfaits et déterminer les temps de vie des phonons. Ensuite, ces derniers sont utilisés pour écrire une équation de transport de Boltzmann pour la densité de phonons dont la résolution donne accès à la conductivité thermique. L'inclusion de défauts ponctuels a pour objectif de réduire la conductivité thermique par diffusion des phonons. Pour modéliser leur effet dans un régime de forte concentration une méthode champ moyen a été développée et appliquée aux half-Heusler. Pour traiter le régime dilué, une méthode faisant appel aux fonctions de Green a été utilisée. Ces deux méthodes montrent que des réductions significatives de conductivité thermique des composés NiTiSn, NiZrSn et NiHfSn sont déjà obtenues pour des concentrations de 10 % en dopants. / Thermoelectric materials provide a way to convert thermal energy into electrical energy. Nonetheless, their low efficiency is the main obstacle for global scale applications. Experimentally, specific treatments can lead to great improvement in the efficiency, mainly by lowering the thermal conductivity. This thesis is aimed at calculating from first principles, the thermal transport properties in perfect and doped half-Heusler thermoelectric materials. We begin with a theoretical analysis of the harmonic and anharmonic properties of phonons for perfect phases.The density functional theory is used to deduce the phonons lifetime from phonon-phonon interactions. The lifetimes are integrated into the Boltzmann transport equation for the phonon density, which solution allows us to compute fully ab initio the lattice thermal conductivity. The purpose of point defects is to scatter the phonons and thus reduce thermal conductivity. We developed two methods to account for the defects on thermal transport. The first one, based on a mean field approach, is suitable for the high concentration regimes. The second one in the framework of Green functions theory is used for dilute regimes. Both methods consistently show that the main reduction of thermal conductivity is already obtained within around 10 % of solute elements in NiTiSn, NiZrSn and NiHfSn.

Abstract After the discovery of topological insulators (TIs), it has come to be widely recognized that topological states of matter can actually be widespread. In this sense, TIs have established a new paradigm about topological materials. Recent years have seen a surge of interest in topological semimetals, which embody two different ways of generalizing the effectively massless electrons to bulk materials. Dirac and, particularly, Weyl semimetals should support several transport and optical phenomena that are still being sought in experiments. A number of promising experimental results indicate superconductivity in members of half-Hesuler semimetals which realize the mixing singlet and triplet pairing symmetry. We now turn to results we got through the work on topological semimetals. This work presents quantum high field transports on Dirac and Weyl topological semimetals including Sr1-yMn1-zSb2 (y, z < 0.1), YbMnBi2 and TaP. In case of Sr1-yMn1-zSb2 (y, z < 0.1), massless relativistic fermion was reported with m* = 0.04-0.05m0. This material presented a ferromagnetic order for in 304 K < T < 565 K, but a canted antiferromagnetic order with a net ferromagnetic component for T < 304 K. These are considered striking features of Dirac fermions For YbMnBi2, we reported the unusual interlayer quantum transport behavior in magnetoresistivity, resulting from the zeroth LL mode observed in this time reversal symmetry breaking type II Weyl semimetal. Also, for Weyl semimetal TaP the measurements probed multiple Fermi pockets, from which nontrivial π Berry phase and Zeeman splitting were extracted. Our ultra-low penetration depth measurements on half-Heuslers YPdBi and TbPdBi revealed a power- law behavior with n= 2.76 ± 0.04 for YPdBi samples and n=2.6 ± 0.3 for TbPdBi sample. We may conclude the exponent n > 2 implies nodless superconducting gap in our samples. Also, we found that despite the increase in magnetic correlations from YPdBi to TbPdBi, superconductivity remains robust in both systems which indicates that AF fluctuations do not play a major role in superconducting mechanism.

Thermoelectric (TE) ZrNiSn samples with a half-Heusler atomic structure were synthesized by mechanical alloying (MA) and consolidation by either Spark Plasma Sintering (SPS) or hot pressing (HP). X-Ray diffraction patterns of as milled powders and consolidated samples were compared and analyzed for phase purity. Thermal conductivity, electrical conductivity and Seebeck coefficient are measured as a function of temperature in the range 300 K to 800 K and compared with measurements reported for high temperature solid state reaction synthesis of this compound. HP samples, compared to SPS samples, demonstrate increased grain growth due to longer heating times. Reduced grain size achieved by MA and SPS causes increased phonon scattering due to the increased number of grain boundaries, which lowers the thermal conductivity without doping the base system with addition phonon scattering centers. Mechanical characterization of the samples by microindentation and depth sensing indentation for hardness and elastic modulus will be discussed.