The anisotropic thermal expansion of boron nitride

Yates, B.; Overy, M. J.; Pirgon, O

doi:10.1080/14786437508221624

Cited by 103 publications

(65 citation statements)

References 17 publications

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“…Although LDA calculations tend to overbind and yield a and c parameter values slightly lower (by 0.4% and 2%, respectively) than the experimental values reported in Refs. [30,31], the quasiharmonic approximation yields a temperature dependence of the lattice parameter in excellent agreement with experiment. Figures 5(a) and 5(b) show the thermal expansion of the a and c parameters relative to their values at zero temperature, compared to experimental values available in the literature.…”

Section: Thermal Lattice Expansionsupporting

confidence: 59%

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

et al. 2018

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Hexagonal boron nitride (h-BN) is a layered crystal that is attracting a great deal of attention as a promising material for nanophotonic applications. The strong optical anisotropy of this crystal is key to exploit polaritonic modes for manipulating light-matter interactions in 2D materials. h-BN has also great potential for solid-state neutron detection and neutron imaging devices, given the exceptionally high thermal neutron capture cross section of the boron-10 isotope. A good knowledge of phonons in layered crystals is essential for harnessing long-lived phonon-polariton modes for nanophotonic applications and may prove valuable for developing solidstate 10 BN neutron detectors with improved device architectures and higher detection efficiencies. Although phonons in graphene and isoelectronic materials with a similar hexagonal layer structure have been studied, the effect of isotopic substitution on the phonons of such lamellar compounds has not been addressed yet. Here we present a Raman scattering study of the in-plane high-energy Raman active mode on isotopically enriched singlecrystal h-BN. Phonon frequency and lifetime are measured in the 80-600-K temperature range for 10 B-enriched, 11 B-enriched, and natural composition high quality crystals. Their temperature dependence is explained in the light of perturbation theory calculations of the phonon self-energy. The effects of crystal anisotropy, isotopic disorder, and anharmonic phonon-decay channels are investigated in detail. The isotopic-induced changes in the phonon density of states are shown to enhance three-phonon anharmonic decay channels in 10 B-enriched crystals, opening the possibility of isotope tuning of the anharmonic phonon decay processes.

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Section: Thermal Lattice Expansionsupporting

confidence: 59%

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

et al. 2018

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“…[25] up to RT by x-ray diffraction using a synchrotron source. For temperatures from RT up to 600 K, the lattice parameter variation was evaluated using the thermal expansion coefficients reported in the interferometric study by Yates et al [28]. The temperature dependence of the thermal frequency shift of the E low 2g phonon calculated by DFT (empty circles in Fig.…”

Section: B Thermal Expansion Effectsmentioning

confidence: 99%

“…lattice constants derived from these x-ray measurements to evaluate the effect of thermal expansion on the temperaturedependent phonon frequency shifts. For temperatures above RT, we use the lattice parameters derived from the temperature dependence of the thermal expansion coefficient reported in an earlier interferometric study [28].…”

Section: A Anisotropic Thermal Expansion Of H-bnmentioning

confidence: 99%

Temperature dependence of Raman-active phonons and anharmonic interactions in layered hexagonal BN

et al. 2016

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We present a Raman scattering study of optical phonons in hexagonal BN for temperatures ranging from 80 to 600 K. The experiments were performed on high-quality, single-crystalline hexagonal BN platelets. The observed temperature dependence of the frequencies and linewidths of both Raman active E 2g optical phonons is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional theory calculations. With increasing temperature, the E high 2g mode displays strong anharmonic interactions, with a linewidth increase that indicates an important contribution of four-phonon processes and a marked frequency downshift that can be attributed to a substantial effect of the four-phonon scattering processes (quartic anharmonicity). In contrast, the E low 2g mode displays a very narrow linewidth and weak anharmonic interactions, with a frequency downshift that is primarily accounted for by the thermal expansion of the interlayer spacing.

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“…4a-c. The coefficient of thermal expansion of the BN is negative (22.9|10 26 /K at 293 K along a axis) 38 compared to BS glass (3.3|10 26 / K). This indicates that during cooling, the BNNSs expanded while the BS matrix shrank, which leads to generation of hoop compression stress around the BNNSs in the nanocomposite.…”

Section: Resultsmentioning

confidence: 99%

Boron nitride nanosheets reinforced glass matrix composites

Saggar

Porwal

Tatarko

et al. 2015

Advances in Applied Ceramics

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The effect of reinforcing boron nitride nanosheets (BNNSs) on the mechanical properties of an amorphous borosilicate glass (BS) matrix was studied. The BNNSs were prepared using liquid exfoliation method and characterised by transmission electron microscopy, scanning electron microscopy and X-ray diffraction (XRD) analysis. The average length was ,0.5 mm, and thickness of the nanosheets was between 4 and 30 layers. These BNNSs were used to prepare BS-BNNS composite with different loading concentrations of 1, 2.5 and 5 mass-% (i.e. 1.395, 3.705 and 7.32 vol.-%). Spark plasma sintering (SPS) was used to densify these composites to avoid structural damages to the BNNSs and/or crystallisation within the composite sample during high temperature processing. The BNNSs were found to be evenly distributed in the composites matrix and were found to be aligned in an orientation perpendicular to the direction of the applied force in SPS. The mechanical properties including fracture toughness, flexural strength and elastic modulus were measured. Both fracture toughness and flexural strength increased linearly with increasing concentration of BNNSs in BS glass. There was an enhancement of ,45% in the fracture toughness (1.10 MPa.m 1/2 ) as well as flexural strength (118.82 MPa) with the addition of only 5 mass-% loading of BNNSs compared to BS glass (0.76 MPa.m 1/2 ; 82.16 MPa). The toughening mechanisms developed in the composites because of the reinforcement of BNNSs were thoroughly investigated.

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The anisotropic thermal expansion of boron nitride

Cited by 103 publications

References 17 publications

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

Temperature dependence of Raman-active phonons and anharmonic interactions in layered hexagonal BN

Boron nitride nanosheets reinforced glass matrix composites

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