scholarly journals Large Piezoelectric Response and Ferroelectricity in Li and V/Nb/Ta co-doped w-AlN

2020 ◽  
Author(s):  
Mohammad Noor-A-Alam ◽  
Oskar Olszewski ◽  
Humberto Campanella ◽  
Michael Nolan
Keyword(s):  
Acoustic Wave ◽  
Density Functional ◽  
Electromechanical Coupling ◽  
Piezoelectric Materials ◽  
Electric Polarization ◽  
Piezoelectric Response ◽  
Co Doping ◽  
Piezoelectric Strain ◽  
Co Doped ◽  
Piezoelectric Strain Constant

<div>Based on density functional theory, we show that Li and</div><div>X (X=V, Nb and Ta) co-doping in 1Li:1X ratio broadens the</div><div>compositional freedom for significant piezoelectric enhancement in w-AlN, promising them to be good alternatives of expensive Sc. Interestingly, these co-doped w-AlN also show quite large spontaneous electric polarization about 0.80 C/m2 with the possibility of ferroelectric polarization switching, opening new possibilities in wurtzite nitrides. Increase in piezoelectric stress constant (e33) with decrease in elastic constant ( C33 ) results enhancement in piezoelectric strain constant ( d33 ), which is desired for improving the performance of resonators for high frequency RF signals. Also, these co-doped w-AlN are potential lead-free piezoelectric materials for energy harvesting and sensors as they improve the longitudinal electromechanical coupling constant (K^2 33), transverse piezoelectric strain constant (d31), and figure of merit for power generation. However, the enhancement in K^2 33 is not as pronounced as that in d33, because co-doping increases the dielectric constant. The longitudinal acoustic wave velocity (7.09 km/s) of Li0.1875Ta0.1875Al0.625N is quite comparable with that of commercially used piezoelectric LiNbO3 or LiTaO3 in special cuts (about 5~7 km/s) despite the fact that the acoustic wave velocities drop with co-doping or Sc concentration.</div>

scholarly journals Large Piezoelectric Response and Ferroelectricity in Li and V/Nb/Ta co-doped w-AlN

2020 ◽  
Author(s):  
Mohammad Noor-A-Alam ◽  
Oskar Olszewski ◽  
Humberto Campanella ◽  
Michael Nolan
Keyword(s):  
Acoustic Wave ◽  
Density Functional ◽  
Electromechanical Coupling ◽  
Piezoelectric Materials ◽  
Electric Polarization ◽  
Piezoelectric Response ◽  
Co Doping ◽  
Piezoelectric Strain ◽  
Co Doped ◽  
Piezoelectric Strain Constant

<div>Based on density functional theory, we show that Li and</div><div>X (X=V, Nb and Ta) co-doping in 1Li:1X ratio broadens the</div><div>compositional freedom for significant piezoelectric enhancement in w-AlN, promising them to be good alternatives of expensive Sc. Interestingly, these co-doped w-AlN also show quite large spontaneous electric polarization about 0.80 C/m2 with the possibility of ferroelectric polarization switching, opening new possibilities in wurtzite nitrides. Increase in piezoelectric stress constant (e33) with decrease in elastic constant ( C33 ) results enhancement in piezoelectric strain constant ( d33 ), which is desired for improving the performance of resonators for high frequency RF signals. Also, these co-doped w-AlN are potential lead-free piezoelectric materials for energy harvesting and sensors as they improve the longitudinal electromechanical coupling constant (K^2 33), transverse piezoelectric strain constant (d31), and figure of merit for power generation. However, the enhancement in K^2 33 is not as pronounced as that in d33, because co-doping increases the dielectric constant. The longitudinal acoustic wave velocity (7.09 km/s) of Li0.1875Ta0.1875Al0.625N is quite comparable with that of commercially used piezoelectric LiNbO3 or LiTaO3 in special cuts (about 5~7 km/s) despite the fact that the acoustic wave velocities drop with co-doping or Sc concentration.</div>

scholarly journals Ferromagnetic 1H-LaBr2 monolayer: a promising 2D piezoelectric

2021 ◽  
Author(s):  
Mohammad Noor A-Alam ◽  
Michael Nolan
Keyword(s):  
Elastic Constants ◽  
Density Functional ◽  
Piezoelectric Materials ◽  
Covalent Bond ◽  
Interatomic Bond ◽  
Piezoelectric Response ◽  
Spintronic Devices ◽  
Mos2 Monolayer ◽  
Piezoelectric Strain ◽  
Ionic Contribution

Abstract The discovery of two dimensional (2D) materials that have excellent piezoelectric response along with intrinsic magnetism is promising for nanoscale multifunctional piezoelectric or spintronic devices. Piezoelectricity requires non-centrosymmetric structures with an electric band-gap, whereas magnetism demands broken time-reversal symmetry. Most of the well-known 2D piezoelectric materials – e.g., 1H-MoS2 monolayer – are not magnetic. Being intrinsically magnetic, semiconducting 1H-LaBr2and 1H-VS2 monolayers can combine magnetism and piezoelectricity. We compare piezoelectric properties of 1H-MoS2, 1H-VS2 and 1H-LaBr2 using density functional theory. Our results show that ferromagnetic 1H-LaBr2 2D monolayer displays a larger piezoelectric strain co-efficient (d_{11}= -4.527 pm/V, which is close to d_{11}= 4.104 pm/V of 1H-VS2 monolayer) compared to that of well-known 1H-MoS2 monolayer (d_{11}= 3.706 pm/V), while 1H-MoS2 monolayer has a larger piezoelectric stress co-efficient (e_{11}= 370.675 pC/m) than the 1H-LaBr2 monolayer (e_{11}= -94.175 pC/m, which is also lower than e_{11}= 298.100 pC/m of 1H-VS2 monolayer). These in-plane piezoelectric d_{11} coefficients are quite comparable with piezo-response of bulk wurtzite nitrides – e.g., d_{33} of GaN is about 3.1 pm/V. The large d_{11} for 1H-LaBr2 monolayer originates from the low elastic constants, C_{11}= 30.338 N/m and C_{12} = 9.534 N/m. Interestingly, the sign of the piezoelectric co-coefficients for 1H-LaBr2 monolayer is different to that of the 1H-MoS2 or 1H-VS2 monolayers. The negative sign arises from the negative ionic contribution of e_{11}, which dominates in the 1H-LaBr2 monolayer, whereas the electronic part of e_{11} dominates in 1H-MoS2 and 1H-VS2. Furthermore, we explain the origin of this large ionic contribution of e_{11} for 1H-LaBr2 in terms of the Born effective charges (Z_{11}) and the sensitivity of the atomic positions to the strain (\frac{du}{d\eta}). Surprisingly, we observe a sign reversal in the Z_{11} of Mo and S compared to the nominal oxidation states, which makes both the electronic and ionic parts of e_{11} positive, and results in the high value of e_{11}. Additionally, our interatomic bond analysis using crystal orbital Hamilton populations indicates that the weaker covalent bond in 1H-LaBr2 monolayer is responsible for large \frac{du}{d\eta} and elastic softening (lower elastic constants).

FLEXOELECTRIC COMPOSITE — A NEW PROSPECT FOR LEAD-FREE PIEZOELECTRICS

2010 ◽  
Vol 03 (01) ◽  
pp. 79-81 ◽  
Author(s):  
BAOJIN CHU ◽  
WENYI ZHU ◽  
NAN LI ◽  
L. ERIC CROSS
Keyword(s):  
Piezoelectric Properties ◽  
Piezoelectric Materials ◽  
Physical Phenomenon ◽  
Mechanical Strain ◽  
Dielectric Materials ◽  
Electric Polarization ◽  
Lead Free ◽  
Piezoelectric Response ◽  
Bst Ceramics ◽  
Better Than

Flexoelectricity describes the physical phenomenon of the generation of electric polarization from mechanical strain gradient in solid insulators. In common dielectric materials, the flexoelectric coefficient is trivially small ~10-10 C/m. In Ba(Sr,Ti)O 3 (BST) ceramics, flexoelectric coefficient up to 10-4 C/m was observed. Such high coefficient makes it possible to design high piezoelectric response flexoelectric composites. In this letter, we will demonstrate that the newly designed flexoelectric composites could have piezoelectric properties better than conventional piezoelectric materials.

Bandgap control and optical properties of β-Si3N4 by single- and co-doping from a first-principles simulation

2018 ◽  
Vol 32 (14) ◽  
pp. 1850178 ◽  
Author(s):  
Xuefeng Lu ◽  
Xu Gao ◽  
Junqiang Ren ◽  
Cuixia Li ◽  
Xin Guo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Blue Shift ◽  
Functional Theory ◽  
Co Doping ◽  
Charge Density Difference ◽  
Co Doped

Bandgap tailoring of [Formula: see text]-Si3N4 is performed by single and co-doping by using density functional theory (DFT) of PBE functional and plane-wave pseudopotential method. The results reveal that a direct bandgap transfers into an indirect one when single-doped with As element. Also, a considerate decrease of bandgap to 0.221 eV and 0.315 eV is present for Al–P and As–P co-doped systems, respectively, exhibiting a representative semiconductor property that is characteristic for a narrower bandgap. Compared with other doped systems, Al-doped system with formation energy of 2.67 eV is present for a more stable structure. From charge density difference (CDD) maps, it is found that the blue area between co-doped atoms increases, illustrating an enhancement of covalent property for Al–P and Al–As bonds. Moreover, a slightly obvious “Blue shift” phenomenon can be obtained in Al, Al–P and Al–As doped systems, indicating an enhanced capacity of responses to light, which contributes to the insight for broader applications with regard to photoelectric devices.

Effect of Co-Doping on Electronic and Magnetic Properties in Ti2NiAl Heusler Alloy

2012 ◽  
Vol 602-604 ◽  
pp. 575-578
Author(s):  
Bo Wu ◽  
Xiu De Yang ◽  
Song Zhang
Keyword(s):  
Heusler Alloy ◽  
Density Functional ◽  
Magnetic Moments ◽  
High Energy ◽  
Type Structure ◽  
Local Spin Density Approximation ◽  
Lattice Constants ◽  
Co Doping ◽  
The Density Functional Theory ◽  
Co Doped

By using local spin density approximation (LSDA) scheme within the density functional theory (DFT), the structure, magnetism and electronic properties of Co-doped Heusler alloy Ti2NiAl with Hg2CuTi- and Cu2MnAl-type structure are comprehensively investigated. The results revealed that whole of the doped alloys with Hg2CuTi-type structure are ground configurations and half-metallic. With the increase of Co-doped concentration, the lattice constants and total magnetic moments in per unit are changed linearly, and the discrepancies of total energy between Hg2CuTi- and Cu2MnAl structure are also enhanced. Analysis on density of states (DOS) revealed that the Fermi level should gradually move to high-energy orientation with increasing Co content due to stronger hybridization of d-electronic atoms.

First-principle study of SO2 adsorption on Fe/Co-doped vacancy defected single-walled (8, 0) carbon nanotubes in sensor applications

2019 ◽  
Vol 18 (05) ◽  
pp. 1950025 ◽  
Author(s):  
Meng Zhang ◽  
Guoqing Li ◽  
Xiaomin Lu ◽  
Qianru Zhang ◽  
Wei Li
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Energy Gap ◽  
Single Vacancy ◽  
Functional Theory ◽  
Sensor Applications ◽  
Co Doping ◽  
So2 Adsorption ◽  
Before And After ◽  
Co Doped

To explore the excellent sensor for detecting the pollution gas [Formula: see text], the adsorptions of [Formula: see text] molecule on the surfaces of Fe/Co-doped carbon nanotubes (CNTs) and single vacancy defected (8, 0) CNTs were investigated by using density functional theory (DFT). In addition, the adsorption energies, geometries, energy gaps and electronic structures were analyzed. The results showed that Fe/Co-doping and single-vacancy-defected can improve the adsorption and sensitiveness of CNTs toward [Formula: see text]. Considering the changes of energy gap before and after the [Formula: see text] molecule adsorbed on each modified CNTs and its adsorption strength, Fe-doped CNTs (Fe-CNTs) and Co-doped site-2 single-vacancy-defected CNTs performed better for detecting [Formula: see text] molecule. With the decreasing number of electrons of the doped atom (Fe, Co, Ni), the adsorption became more stable. The results of this paper are profound and meaningful for designing [Formula: see text] sensing devices.

scholarly journals Giant electromechanical coupling of relaxor ferroelectrics controlled by polar nanoregion vibrations

2016 ◽  
Vol 2 (9) ◽  
pp. e1501814 ◽  
Author(s):  
Michael E. Manley ◽  
Douglas L. Abernathy ◽  
Raffi Sahul ◽  
Daniel E. Parshall ◽  
Jeffrey W. Lynn ◽  
...  
Keyword(s):  
Local Structure ◽  
Electromechanical Coupling ◽  
Collective Motion ◽  
Piezoelectric Materials ◽  
Relaxor Ferroelectrics ◽  
Piezoelectric Response ◽  
Atomic Displacements ◽  
Electromechanical Responses ◽  
Polar Nanoregions ◽  
Ultrasound Applications

Relaxor-based ferroelectrics are prized for their giant electromechanical coupling and have revolutionized sensor and ultrasound applications. A long-standing challenge for piezoelectric materials has been to understand how these ultrahigh electromechanical responses occur when the polar atomic displacements underlying the response are partially broken into polar nanoregions (PNRs) in relaxor-based ferroelectrics. Given the complex inhomogeneous nanostructure of these materials, it has generally been assumed that this enhanced response must involve complicated interactions. By using neutron scattering measurements of lattice dynamics and local structure, we show that the vibrational modes of the PNRs enable giant coupling by softening the underlying macrodomain polarization rotations in relaxor-based ferroelectric PMN-xPT {(1 − x)[Pb(Mg1/3Nb2/3)O3] – xPbTiO3} (x = 30%). The mechanism involves the collective motion of the PNRs with transverse acoustic phonons and results in two hybrid modes, one softer and one stiffer than the bare acoustic phonon. The softer mode is the origin of macroscopic shear softening. Furthermore, a PNR mode and a component of the local structure align in an electric field; this further enhances shear softening, revealing a way to tune the ultrahigh piezoelectric response by engineering elastic shear softening.

Band-gap tuning of graphene by Be doping and Be, B co-doping: a DFT study

RSC Advances ◽  
2015 ◽  
Vol 5 (69) ◽  
pp. 55762-55773 ◽  
Author(s):  
Saif Ullah ◽  
Akhtar Hussain ◽  
WaqarAdil Syed ◽  
Muhammad Adnan Saqlain ◽  
Idrees Ahmad ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Co Doping ◽  
Structural And Electronic Properties ◽  
Doped Graphene ◽  
Band Gap Tuning ◽  
Co Doped

First-principles density functional theory (DFT) calculations were carried out to investigate the structural and electronic properties of beryllium (Be) doped and, Be with boron (B) co-doped graphene systems.

Theoretical investigation of Er-O co-doping in hexagonal GaN

2011 ◽  
Vol 1342 ◽  
Author(s):  
Simone Sanna ◽  
Uwe Gerstmann ◽  
Wolf Gero Schmidt
Keyword(s):  
Binding Energy ◽  
Density Functional ◽  
Electronic Charge ◽  
High Binding Energy ◽  
Oxygen Ions ◽  
Co Doping ◽  
Geometric Configurations ◽  
Similar Formation ◽  
Formation Energies ◽  
Co Doped

ABSTRACTThe co-doping of hexagonal GaN with Er and O is investigated by means of density functional calculations. Predominantly Er-O defect-pairs characterized by a binding energy around 0.5 eV are formed. Different geometric configurations with various orientations (i.e. axial and basal pairs with C3v or C1h symmetry) are expected with similar formation energies. Independent of the particular configuration, the presence of oxygen does not deeply affect the atomic structure and the electronic charge distribution around the Er centers. The relatively high binding energy suggests that Er-O pairs should survive thermal treatment. An investigation of the binding energy per bond indicates that on the other hand Er-Ox complexes (x=2,3,4) are not likely to be formed (differently from Er-O co-doped Si). Rather, as long as the oxygen fluence does not overtake the Er fluence, different oxygen ions will be bound to different Er-centers.

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