Materials design and development of functional materials for industry

Asahi, Ryoji; Morikawa, Takeshi; Hazama, Hirofumi; Matsubara, Masahiro

doi:10.1088/0953-8984/20/6/064227

Cited by 20 publications

(24 citation statements)

References 40 publications

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“…[ 56 ] And Asahi et al reported a liquid quench approach followed by SPS to prepare HH compounds with improved homogeneity and TE properties. [ 57 ] Birkel et al used microwave heating to prepare TiNiSn and TiCoSb, reducing the reaction time signifi cantly from more than a week to one minute. [ 58 ] A combined ball milling and hot pressing approach was adopted to obtain nanostructured HH alloys by Yan et al [ 59 ] Nevertheless, impurity phase is still an obstacle for these methods to rapidly obtain high quality products.…”

Section: Rapid Fabrication and Atomic Disordersmentioning

confidence: 99%

High Efficiency Half‐Heusler Thermoelectric Materials for Energy Harvesting

Zhu

Xie

et al. 2015

Advanced Energy Materials

428

261

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respectively the temperature of the hot side and cold side, Δ T = T H -T C and T avg are the temperature gradient and average between hot and cold sides. [ 4 ] The fi gure of merit zT is defi ned as zT = α 2 σT /( κ e + κ L ), where α , σ , T , κ e and κ L are respectively the Seebeck coeffi cient, the electrical conductivity, the absolute temperature, and the electrical and lattice components of total thermal conductivity κ . [ 2 ] High conversion effi ciency of 15%-20% is thought of as the "Holy Grail" for large scale application of TE technologies. [ 5 ] As depicted in Figure 1 , this conversion efficiency can be realized by using middle temperature (500-900 K) TE materials with very high zT or high temperature (>900 K) TE materials with compromised zT . Recently, much progress has been made in developing high effi ciency middle temperature TE materials: high zT 's of ≈1.5 at 750 K for n-type and ≈2.0 at for p-type have been achieved in PbTe-based alloys, [6][7][8][9] while n-type and p-type fi lled skutterudites have the maximum zT 's of ≈1.7 and ≈1.0, respectively, near 800 K. [ 10,11 ] Some other TE materials made of earth-abundant and non-toxic elements have also been identifi ed, such as single crystal SnSe ( zT ≈ 2.6 at 923 K), [ 12 ] silicides [ 13,14 ] and α -MgAgSb. [ 15 ] However, there remain tremendous challenges for most of these TE materials for large scale commercial application, mainly due to their relatively poor thermal stability and weak mechanical strength at high temperatures. In Half-Heusler (HH) compounds have gained ever-increasing popularity as promising high temperature thermoelectric materials. High fi gure of merit zT of ≈1.0 above 1000 K has recently been realized for both n-type and p-type HH compounds, demonstrating the realistic prospect of these high temperature compounds for high effi ciency power generation. Here, recent progress in advanced fabrication techniques and the intrinsic atomic disorders in HH compounds, which are linked to the understanding of the electrical transport, is discussed. Thermoelectric transport features of n-type ZrNiSn-based HH alloys are particularly emphasized, which is benefi cial to further improving thermoelectric performance and comprehensively understanding the underlying mechanisms in HH thermoelectric materials. The rational design and realization of new high performance p-type Fe(V,Nb)Sb-based HH compounds are also demonstrated. The outlook for future research directions of HH thermoelectric materials is also discussed.

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Section: Rapid Fabrication and Atomic Disordersmentioning

confidence: 99%

High Efficiency Half‐Heusler Thermoelectric Materials for Energy Harvesting

Zhu

Xie

et al. 2015

Advanced Energy Materials

428

261

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“…Despite the wealth of literature on N-doped TiO 2 , 6 there is little consensus on whether this leads to an overall improvement in sunlight driven photocatalysis. [7][8][9][10][11][12] Cationic dopants with a higher oxidation state than Ti 4+ do not reduce the visible light response of anatase TiO 2 . Instead they act as electron donors, injecting electrons into the conduction band, and can transform anatase into a transparent conducting oxide (TCO).…”

Section: Introductionmentioning

confidence: 99%

Multifunctional P-Doped TiO₂ Films: A New Approach to Self-Cleaning, Transparent Conducting Oxide Materials

et al. 2015

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Multifunctional P-doped TiO 2 thin-films were synthesised by atmospheric pressure chemical vapour deposition (APCVD). This is the first example of P-doped TiO 2 films with both P 5+ and P 3-states, with the relative proportion being determined by synthesis conditions. This technique to control the oxidation state of the impurities presents a new approach to achieve films with both self-cleaning and TCO properties. The origin of electrical conductivity in these materials was correlated to the incorporation of P 5+ species, as suggested by Hall Effect probe measurements. The photocatalytic performance of the films was investigated using the model organic pollutant, stearic acid, with films containing predominately P 3-states found to be vastly inferior photocatalysts compared to undoped TiO 2 films. Transient absorption spectroscopy studies also showed that charge carrier concentrations increased by several orders of magnitude in films containing P 5+ species only, whereas photo-generated carrier lifetimesand thus photocatalytic activity, were severely reduced upon incorporation of P 3-species. The results presented here provide important insights on the influence of dopant nature and location within a semiconductor structure. These new P-doped TiO 2 films are a breakthrough in the development of multifunctional advanced materials with tuned properties for a wide range of applications.

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“…The prolific work reported by Asahi et al [1] in which nitrogen doping was identified as a promising approach for an effective bandgap narrowing of TiO 2 has spawned active discussion and controversy in the last decade [2][3][4][5][6]. For the most part, the discussion around nitrogen-doped TiO 2 materials (henceforth N-TiO 2 ) has been focused on their visible light activity and its origins.…”

Section: Introductionmentioning

confidence: 99%

Critical influence of surface nitrogen species on the activity of N-doped TiO2 thin-films during photodegradation of stearic acid under UV light irradiation

Quesada-Cabrera

Sotelo-Vázquez

Darr

et al. 2014

Applied Catalysis B: Environmental

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a b s t r a c tAtmospheric-pressure chemical vapour deposition (APCVD) was used to produce a series of nitrogendoped titania (N-TiO 2 ) thin-films using tert-butylamine as the nitrogen source. The films were deposited as the anatase phase on glass and quartz substrates and characterised using X-ray diffraction, optical and vibrational spectroscopy and electron microscopy. The nature and location of the nitrogen species present on the surface and bulk of the films was studied by X-ray photoelectron spectroscopy. Thorough comparison amongst films with similar structural and morphological features allowed the role of nitrogen species to be evaluated during photo-oxidation of a model organic pollutant (stearic acid). Sequential photocatalytic experiments revealed a drastic decrease in the UV activity of the films which were correlated with changes involving surface nitrogen groups. The existence of concomitant nitrogen species with similar binding energies (ca. 400 eV) but different chemical nature is proposed, as well as the direct participation of at least one of these species in the oxidation reaction. A similar mechanism for the visible light activity of N-TiO 2 materials is also suggested.

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Materials design and development of functional materials for industry

Cited by 20 publications

References 40 publications

High Efficiency Half‐Heusler Thermoelectric Materials for Energy Harvesting

High Efficiency Half‐Heusler Thermoelectric Materials for Energy Harvesting

Multifunctional P-Doped TiO₂ Films: A New Approach to Self-Cleaning, Transparent Conducting Oxide Materials

Critical influence of surface nitrogen species on the activity of N-doped TiO2 thin-films during photodegradation of stearic acid under UV light irradiation

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Materials design and development of functional materials for industry

Cited by 20 publications

References 40 publications

High Efficiency Half‐Heusler Thermoelectric Materials for Energy Harvesting

High Efficiency Half‐Heusler Thermoelectric Materials for Energy Harvesting

Multifunctional P-Doped TiO2 Films: A New Approach to Self-Cleaning, Transparent Conducting Oxide Materials

Critical influence of surface nitrogen species on the activity of N-doped TiO2 thin-films during photodegradation of stearic acid under UV light irradiation

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Product

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Multifunctional P-Doped TiO₂ Films: A New Approach to Self-Cleaning, Transparent Conducting Oxide Materials