Lowell Miyagi - Academia.edu (original) (raw)
Papers by Lowell Miyagi
Powder Diffraction, 2014
Synchrotron X-ray diffraction images are increasingly used to characterize crystallographic prefe... more Synchrotron X-ray diffraction images are increasingly used to characterize crystallographic preferred orientation distributions (texture) of fine-grained polyphase materials. Diffraction images can be analyzed quantitatively with the Rietveld method as implemented in the software package Materials Analysis Using Diffraction. Here we describe the analysis procedure for diffraction images collected with high energy X-rays for a complex, multiphase shale, and for those collected in situ in diamond anvil cells at high pressure and anisotropic stress.
The Review of scientific instruments, 2013
In order to generate homogeneous high temperatures at high pressures, a ring-shaped graphite heat... more In order to generate homogeneous high temperatures at high pressures, a ring-shaped graphite heater has been developed to resistively heat diamond-anvil cell (DAC) samples up to 1300 K. By putting the heater in direct contact with the diamond anvils, this graphite heater design features the following advantages: (1) efficient heating: sample can be heated to 1300 K while the DAC body temperature remains less than 800 K, eliminating the requirement of a special alloy for the DAC; (2) compact design: the sample can be analyzed with in situ measurements, e.g., x-ray, optical, and electrical probes are possible. In particular, the side access of the heater allows for radial x-ray diffraction (XRD) measurements in addition to traditional axial XRD.
At near ambient conditions, CaIrO 3 is isostructural with the high-pressure polymorph MgSiO 3 "po... more At near ambient conditions, CaIrO 3 is isostructural with the high-pressure polymorph MgSiO 3 "post-perovskite" (pPv). MgSiO 3 pPv is thought to be a major phase in the earth's lowermost mantle. CaIrO 3 can thus serve as an analog for studying deformation of the pPv phase under conditions achievable with a multi-anvil deformation apparatus. Here we study the rheologic behavior of CaIrO 3 pPv at a variety of pressure and temperature conditions from 2 GPa to 6 GPa and 300 K to 1300 K and various strain rates. Sintered, polycrystalline CaIrO 3 pPv, cylindrical in shape, was deformed in the D-DIA multi-anvil press in several shortening cycles up to 20% axial strain at each temperature and pressure. Shortening cycles were followed by lengthening back to 0% strain. Quantitative texture information was obtained using in-situ synchrotron X-ray diffraction and the Rietveld method to analyze images. In all cases we find that (010) lattice planes align perpendicular to the compression direction upon shortening, and that there is little change in texture with temperature or pressure. This texture pattern is consistent with slip on (010) [100]. The texture observed here is different from that produced in room temperature diamond anvil cell (DAC) experiments on MgGeO 3 and MgSiO 3 pPv which both display textures of (100) and {110} lattice planes at high angles to the compression direction. This implies that CaIrO 3 pPv may not be a good analog for the plastic behavior of MgSiO 3 pPv.
The D 00 region that lies just above the core mantle boundary exhibits complex anisotropy that th... more The D 00 region that lies just above the core mantle boundary exhibits complex anisotropy that this is likely due to preferred orientation (texturing) of the constituent minerals. (Mg,Fe)SiO 3 post-perovskite is widely thought to be the major mineral phase of the D 00 . Texture development has been studied in various post-perovskite phases (MgSiO 3 , MgGeO 3 , and CaIrO 3 ), and different results were obtained. To clarify this controversy, we report on transformation and deformation textures in MgGeO 3 post-perovskite synthesized and deformed at room temperature in the diamond anvil cell. Transformed from the enstatite phase, MgGeO 3 post-perovskite exhibits a transformation texture characterized by (100) planes at high angles to the direction of compression. Upon subsequent deformation, this texture changes and (001) lattice planes become oriented nearly perpendicular to compression, consistent with dominant (001)[100] slip. When MgGeO 3 post-perovskite is synthesized from the perovskite phase, a different transformation texture is observed. This texture has (001) planes at high angle to compression and becomes slightly stronger upon compression. We also find that the yield strength of MgGeO 3 post-perovskite is dependent on grain size and texture. Finer-grained samples exhibit higher yield strength and are harder to induce plastic deformation. Strong textures also affect the yield strength and can result in higher differential stresses. The inferred dominant (001) slip for pPv is significant for geophysics, because, when applied to geodynamic convection models, it predicts the observed anisotropies of S-waves as well as an anti-correlation between P-and S-waves.
Texture analysis of binary mixtures of MgGeO3 and (Mg, Fe) O at in situ high pressure and temperature in the resistive-heated radial diamond anvil cell
Texture Development in Binary Mixtures of Lower Mantle Perovskite and Ferropericlase at High Pressures and Temperatures
High-pressure/high-temperature radial XRD of low-spin ferropericlase
Deformation of MgSiO3 perovskite at high pressure using diamond anvil cells and in-situ radial diffraction
Magnesium silicate perovskite is thought to be the major constituent of the lower mantle. Consequ... more Magnesium silicate perovskite is thought to be the major constituent of the lower mantle. Consequently, knowledge of the deformation behavior of MgSiO3 perovskite is important for understanding the geodynamic behavior in the deep Earth as well as interpreting observed seismic anisotropy. One mechanism that can generate anisotropy is dislocation glide and associated development of texture or lattice preferred orientation (LPO).
Brillouin scattering and preferred orientation of polycrystalline MgO at high-pressure
Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way t... more Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way to obtain aggregate (bulk and shear) moduli of candidate mantle minerals which can be related to seismological observables. However, several poorly understood processes might affect the derived sound wave velocities, including a preferred orientation of the crystallites (texturing) under non-hydrostatic compression in the diamond-anvil cell. Brillouin scattering
Transformation and deformation textures in MgGeO3 post-perovskite: Implications for D''anisotropy
The D'' region which lies just above the core mantle boundary is an incredibly co... more The D'' region which lies just above the core mantle boundary is an incredibly complicated region of the deep Earth, exhibiting heterogeneity, topographic variations and seismic anisotropy. It has been suggested that observed anisotropies are due to preferred orientation (texturing) of the constituent minerals. It is widely thought that the post-perovskite phase of (Mg,Fe)SiO3 is the major mineral phase of
Plastic deformation of polycrystalline MgO up to 1250 K and 65 GPa
Understanding the development of lattice preferred orientations (LPO) in polycrystals is critical... more Understanding the development of lattice preferred orientations (LPO) in polycrystals is critical to constrain the anisotropy and dynamics of the Earth mantle. Until recently, it was not possible to study LPO under high pressure and high temperature. The introduction of the deformation-DIA (D-DIA) and radial diffraction experiments in the diamond anvil cell (DAC) have extended the range of pressures and
Brillouin scattering and radial x-ray diffraction of polycrystalline MgO to 30GPa
Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way t... more Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way to obtain aggregate (bulk and shear) moduli of candidate mantle minerals which can be related to seismological observables. However, several poorly understood processes might affect the derived sound wave velocities, including a preferred orientation of the crystallites (texturing), non-hydrostatic conditions in the diamond-anvil cell and contributions of
Deformation of MgSiO3 Post-Perovskite and D''Anisotropy
In contrast to the bulk of the lower mantle, the D'' region which lies just above... more In contrast to the bulk of the lower mantle, the D'' region which lies just above the core mantle boundary exhibits considerable seismic complexity including seismic discontinuity, large topographic variations, significant lateral heterogeneity, anisotropy and ultra low velocity zones. It is likely that observed anisotropies are due to preferred orientation (texturing) of the constituent minerals. (Mg,Fe)SiO3 post-perovskite (pPv) is widely
Texture development in FeO across the cubic to rhombohedral phase transition
ABSTRACT At ambient conditions, magnesiowüstite (MgxFe1-x)O, one of the major mineral phases in t... more ABSTRACT At ambient conditions, magnesiowüstite (MgxFe1-x)O, one of the major mineral phases in the lower mantle, crystallizes in the rock-salt NaCl (B1) structure. When compressed in a diamond anvil cell (DAC), magnesiowüstite crystals increasingly align their <100> axes with the compression direction. At high pressure ( 18 GPa for x=0, and 35 GPa for x=0.8 and room temperature) a phase transition from cubic to rhombohedral symmetry occurs via compression of three cube body diagonals relative to the fourth. The goal of this investigation is to explore orientation relationships during the phase transition. We compressed wüstite (MgxFe1-x)O with x ≤ 0.10 in a series of DAC experiments at beamline 12.2.2 of the Advanced Light Source in radial geometry at both ambient temperature and high temperature using a combination of resistive and laser heating. Diffraction images were analyzed using the Rietveld method to obtain quantitative texture information. The {001}c in cubic becomes {01-12}r in rhombohedral. On the other hand, {111}c lattice vectors in the cubic phase split into (0003)r and {10-11}r in the rhombohedral phase, and {110}c splits into {11-20}r and {10-14}r. Correspondingly, the diffraction peaks split. After the phase transition, {001}c → {01-12}r is a maximum in the compression direction with only minor trigonality in the inverse pole figure. However, there is clear rhombohedral variant selection with {110}c → {11-20}r having a much stronger maximum than {110}c → {10-14}r. This variant selection may be because elastically softer crystal directions align with the compression direction and would be more thermodynamically stable. Unfortunately the elastic constants of rhombohedral FeO are not yet known to confirm this hypothesis. Conversely the variant selection may be due to progressive deformation of the rhombohedral phase with different slip system activities. This has been investigated with polycrystal plasticity simulations which produce good agreement with experiments if the {10-11}<-12-10>r variant of the cubic {111}<1-10>c is preferentially activated.
Resistive Heating in Radial Geometry Diamond Anvil Cell
Radial X-Ray Diffraction at the Extreme Conditions Beamline of PETRA III: In-Situ Texture Analysis of a Mixture of Perovskite and Ferropericlase to 1100 K and 40 GPa
Strength of (Mg, Fe) O Ferropericlase in Earth's Lower Mantle
Two-phase deformation of lower mantle mineral analogs
Plastic anisotropy and slip systems in ringwoodite deformed to high shear strain in the Rotational Drickamer Apparatus
ABSTRACT High shear strain deformation experiments up to equivalent strains of 180% were performe... more ABSTRACT High shear strain deformation experiments up to equivalent strains of 180% were performed on ringwoodite at conditions of 23 GPa and 1800 K. At very large shear strains, deviation in the strengths of the (3 1 1) and (4 0 0) lattice planes is observed, indicating plastic anisotropy. Lattice strain theory was applied to calculate effective viscosities of the available slip systems from the observed plastic anisotropy. We find that the effective viscosities (unitless) are proportional to 0.43, 0.46, and 1.54 for the {1 1 1}〈11¯0〉, {11¯0}〈1 1 0〉 and {0 0 1}〈11¯0〉 slip systems respectively. This indicates that {1 1 1}〈11¯0〉 slip is slightly softer than {11¯0}〈11¯0〉 at these conditions. Additionally the {1 1 1}〈11¯0〉 slip system has significantly more symmetric variants than the slip systems involving other lattice planes, thus it is expected to dominate deformation. This is confirmed by polycrystal plasticity modeling using the viscoplastic self-consistent code (VPSC) which indicates that simulations with dominant {1 1 1}〈11¯0〉 slip provide the best match to experimental textures.
Resistively-heated diamond-anvil cell to temperatures greater than 1800 K
ABSTRACT Generation of homogeneous high temperatures in the diamond-anvil cell (DAC) has been a g... more ABSTRACT Generation of homogeneous high temperatures in the diamond-anvil cell (DAC) has been a great challenge over the past several decades. Aiming to overcome the disadvantages of small heating areas (<30um) and large temperature gradients (>100K/um) inherent in the laser-heated DAC as well as the limited pressure range (<60GPa) in multi-anvil press experiments, we have developed an externally resistive-heated DAC to produce uniform high temperatures at high pressures. In this study, we modify a previous design employing graphite sheets (Liermann et al., RSI, 2009) with a ring-shaped graphite heater. In a pilot run, we successfully generated temperatures of ~1800 K at a pressure of 20 GPa before the R-type thermocouple melted. These conditions can be extended to higher temperatures and pressures with the use of a C-type thermocouple or spectroradiometry to measure temperature. This technique will open doors to studying material properties, particularly melting, transport and elasticity at high temperatures and pressures.
Powder Diffraction, 2014
Synchrotron X-ray diffraction images are increasingly used to characterize crystallographic prefe... more Synchrotron X-ray diffraction images are increasingly used to characterize crystallographic preferred orientation distributions (texture) of fine-grained polyphase materials. Diffraction images can be analyzed quantitatively with the Rietveld method as implemented in the software package Materials Analysis Using Diffraction. Here we describe the analysis procedure for diffraction images collected with high energy X-rays for a complex, multiphase shale, and for those collected in situ in diamond anvil cells at high pressure and anisotropic stress.
The Review of scientific instruments, 2013
In order to generate homogeneous high temperatures at high pressures, a ring-shaped graphite heat... more In order to generate homogeneous high temperatures at high pressures, a ring-shaped graphite heater has been developed to resistively heat diamond-anvil cell (DAC) samples up to 1300 K. By putting the heater in direct contact with the diamond anvils, this graphite heater design features the following advantages: (1) efficient heating: sample can be heated to 1300 K while the DAC body temperature remains less than 800 K, eliminating the requirement of a special alloy for the DAC; (2) compact design: the sample can be analyzed with in situ measurements, e.g., x-ray, optical, and electrical probes are possible. In particular, the side access of the heater allows for radial x-ray diffraction (XRD) measurements in addition to traditional axial XRD.
At near ambient conditions, CaIrO 3 is isostructural with the high-pressure polymorph MgSiO 3 "po... more At near ambient conditions, CaIrO 3 is isostructural with the high-pressure polymorph MgSiO 3 "post-perovskite" (pPv). MgSiO 3 pPv is thought to be a major phase in the earth's lowermost mantle. CaIrO 3 can thus serve as an analog for studying deformation of the pPv phase under conditions achievable with a multi-anvil deformation apparatus. Here we study the rheologic behavior of CaIrO 3 pPv at a variety of pressure and temperature conditions from 2 GPa to 6 GPa and 300 K to 1300 K and various strain rates. Sintered, polycrystalline CaIrO 3 pPv, cylindrical in shape, was deformed in the D-DIA multi-anvil press in several shortening cycles up to 20% axial strain at each temperature and pressure. Shortening cycles were followed by lengthening back to 0% strain. Quantitative texture information was obtained using in-situ synchrotron X-ray diffraction and the Rietveld method to analyze images. In all cases we find that (010) lattice planes align perpendicular to the compression direction upon shortening, and that there is little change in texture with temperature or pressure. This texture pattern is consistent with slip on (010) [100]. The texture observed here is different from that produced in room temperature diamond anvil cell (DAC) experiments on MgGeO 3 and MgSiO 3 pPv which both display textures of (100) and {110} lattice planes at high angles to the compression direction. This implies that CaIrO 3 pPv may not be a good analog for the plastic behavior of MgSiO 3 pPv.
The D 00 region that lies just above the core mantle boundary exhibits complex anisotropy that th... more The D 00 region that lies just above the core mantle boundary exhibits complex anisotropy that this is likely due to preferred orientation (texturing) of the constituent minerals. (Mg,Fe)SiO 3 post-perovskite is widely thought to be the major mineral phase of the D 00 . Texture development has been studied in various post-perovskite phases (MgSiO 3 , MgGeO 3 , and CaIrO 3 ), and different results were obtained. To clarify this controversy, we report on transformation and deformation textures in MgGeO 3 post-perovskite synthesized and deformed at room temperature in the diamond anvil cell. Transformed from the enstatite phase, MgGeO 3 post-perovskite exhibits a transformation texture characterized by (100) planes at high angles to the direction of compression. Upon subsequent deformation, this texture changes and (001) lattice planes become oriented nearly perpendicular to compression, consistent with dominant (001)[100] slip. When MgGeO 3 post-perovskite is synthesized from the perovskite phase, a different transformation texture is observed. This texture has (001) planes at high angle to compression and becomes slightly stronger upon compression. We also find that the yield strength of MgGeO 3 post-perovskite is dependent on grain size and texture. Finer-grained samples exhibit higher yield strength and are harder to induce plastic deformation. Strong textures also affect the yield strength and can result in higher differential stresses. The inferred dominant (001) slip for pPv is significant for geophysics, because, when applied to geodynamic convection models, it predicts the observed anisotropies of S-waves as well as an anti-correlation between P-and S-waves.
Texture analysis of binary mixtures of MgGeO3 and (Mg, Fe) O at in situ high pressure and temperature in the resistive-heated radial diamond anvil cell
Texture Development in Binary Mixtures of Lower Mantle Perovskite and Ferropericlase at High Pressures and Temperatures
High-pressure/high-temperature radial XRD of low-spin ferropericlase
Deformation of MgSiO3 perovskite at high pressure using diamond anvil cells and in-situ radial diffraction
Magnesium silicate perovskite is thought to be the major constituent of the lower mantle. Consequ... more Magnesium silicate perovskite is thought to be the major constituent of the lower mantle. Consequently, knowledge of the deformation behavior of MgSiO3 perovskite is important for understanding the geodynamic behavior in the deep Earth as well as interpreting observed seismic anisotropy. One mechanism that can generate anisotropy is dislocation glide and associated development of texture or lattice preferred orientation (LPO).
Brillouin scattering and preferred orientation of polycrystalline MgO at high-pressure
Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way t... more Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way to obtain aggregate (bulk and shear) moduli of candidate mantle minerals which can be related to seismological observables. However, several poorly understood processes might affect the derived sound wave velocities, including a preferred orientation of the crystallites (texturing) under non-hydrostatic compression in the diamond-anvil cell. Brillouin scattering
Transformation and deformation textures in MgGeO3 post-perovskite: Implications for D''anisotropy
The D'' region which lies just above the core mantle boundary is an incredibly co... more The D'' region which lies just above the core mantle boundary is an incredibly complicated region of the deep Earth, exhibiting heterogeneity, topographic variations and seismic anisotropy. It has been suggested that observed anisotropies are due to preferred orientation (texturing) of the constituent minerals. It is widely thought that the post-perovskite phase of (Mg,Fe)SiO3 is the major mineral phase of
Plastic deformation of polycrystalline MgO up to 1250 K and 65 GPa
Understanding the development of lattice preferred orientations (LPO) in polycrystals is critical... more Understanding the development of lattice preferred orientations (LPO) in polycrystals is critical to constrain the anisotropy and dynamics of the Earth mantle. Until recently, it was not possible to study LPO under high pressure and high temperature. The introduction of the deformation-DIA (D-DIA) and radial diffraction experiments in the diamond anvil cell (DAC) have extended the range of pressures and
Brillouin scattering and radial x-ray diffraction of polycrystalline MgO to 30GPa
Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way t... more Brillouin scattering on polycrystalline materials at high-pressures promises to be a direct way to obtain aggregate (bulk and shear) moduli of candidate mantle minerals which can be related to seismological observables. However, several poorly understood processes might affect the derived sound wave velocities, including a preferred orientation of the crystallites (texturing), non-hydrostatic conditions in the diamond-anvil cell and contributions of
Deformation of MgSiO3 Post-Perovskite and D''Anisotropy
In contrast to the bulk of the lower mantle, the D'' region which lies just above... more In contrast to the bulk of the lower mantle, the D'' region which lies just above the core mantle boundary exhibits considerable seismic complexity including seismic discontinuity, large topographic variations, significant lateral heterogeneity, anisotropy and ultra low velocity zones. It is likely that observed anisotropies are due to preferred orientation (texturing) of the constituent minerals. (Mg,Fe)SiO3 post-perovskite (pPv) is widely
Texture development in FeO across the cubic to rhombohedral phase transition
ABSTRACT At ambient conditions, magnesiowüstite (MgxFe1-x)O, one of the major mineral phases in t... more ABSTRACT At ambient conditions, magnesiowüstite (MgxFe1-x)O, one of the major mineral phases in the lower mantle, crystallizes in the rock-salt NaCl (B1) structure. When compressed in a diamond anvil cell (DAC), magnesiowüstite crystals increasingly align their <100> axes with the compression direction. At high pressure ( 18 GPa for x=0, and 35 GPa for x=0.8 and room temperature) a phase transition from cubic to rhombohedral symmetry occurs via compression of three cube body diagonals relative to the fourth. The goal of this investigation is to explore orientation relationships during the phase transition. We compressed wüstite (MgxFe1-x)O with x ≤ 0.10 in a series of DAC experiments at beamline 12.2.2 of the Advanced Light Source in radial geometry at both ambient temperature and high temperature using a combination of resistive and laser heating. Diffraction images were analyzed using the Rietveld method to obtain quantitative texture information. The {001}c in cubic becomes {01-12}r in rhombohedral. On the other hand, {111}c lattice vectors in the cubic phase split into (0003)r and {10-11}r in the rhombohedral phase, and {110}c splits into {11-20}r and {10-14}r. Correspondingly, the diffraction peaks split. After the phase transition, {001}c → {01-12}r is a maximum in the compression direction with only minor trigonality in the inverse pole figure. However, there is clear rhombohedral variant selection with {110}c → {11-20}r having a much stronger maximum than {110}c → {10-14}r. This variant selection may be because elastically softer crystal directions align with the compression direction and would be more thermodynamically stable. Unfortunately the elastic constants of rhombohedral FeO are not yet known to confirm this hypothesis. Conversely the variant selection may be due to progressive deformation of the rhombohedral phase with different slip system activities. This has been investigated with polycrystal plasticity simulations which produce good agreement with experiments if the {10-11}<-12-10>r variant of the cubic {111}<1-10>c is preferentially activated.
Resistive Heating in Radial Geometry Diamond Anvil Cell
Radial X-Ray Diffraction at the Extreme Conditions Beamline of PETRA III: In-Situ Texture Analysis of a Mixture of Perovskite and Ferropericlase to 1100 K and 40 GPa
Strength of (Mg, Fe) O Ferropericlase in Earth's Lower Mantle
Two-phase deformation of lower mantle mineral analogs
Plastic anisotropy and slip systems in ringwoodite deformed to high shear strain in the Rotational Drickamer Apparatus
ABSTRACT High shear strain deformation experiments up to equivalent strains of 180% were performe... more ABSTRACT High shear strain deformation experiments up to equivalent strains of 180% were performed on ringwoodite at conditions of 23 GPa and 1800 K. At very large shear strains, deviation in the strengths of the (3 1 1) and (4 0 0) lattice planes is observed, indicating plastic anisotropy. Lattice strain theory was applied to calculate effective viscosities of the available slip systems from the observed plastic anisotropy. We find that the effective viscosities (unitless) are proportional to 0.43, 0.46, and 1.54 for the {1 1 1}〈11¯0〉, {11¯0}〈1 1 0〉 and {0 0 1}〈11¯0〉 slip systems respectively. This indicates that {1 1 1}〈11¯0〉 slip is slightly softer than {11¯0}〈11¯0〉 at these conditions. Additionally the {1 1 1}〈11¯0〉 slip system has significantly more symmetric variants than the slip systems involving other lattice planes, thus it is expected to dominate deformation. This is confirmed by polycrystal plasticity modeling using the viscoplastic self-consistent code (VPSC) which indicates that simulations with dominant {1 1 1}〈11¯0〉 slip provide the best match to experimental textures.
Resistively-heated diamond-anvil cell to temperatures greater than 1800 K
ABSTRACT Generation of homogeneous high temperatures in the diamond-anvil cell (DAC) has been a g... more ABSTRACT Generation of homogeneous high temperatures in the diamond-anvil cell (DAC) has been a great challenge over the past several decades. Aiming to overcome the disadvantages of small heating areas (<30um) and large temperature gradients (>100K/um) inherent in the laser-heated DAC as well as the limited pressure range (<60GPa) in multi-anvil press experiments, we have developed an externally resistive-heated DAC to produce uniform high temperatures at high pressures. In this study, we modify a previous design employing graphite sheets (Liermann et al., RSI, 2009) with a ring-shaped graphite heater. In a pilot run, we successfully generated temperatures of ~1800 K at a pressure of 20 GPa before the R-type thermocouple melted. These conditions can be extended to higher temperatures and pressures with the use of a C-type thermocouple or spectroradiometry to measure temperature. This technique will open doors to studying material properties, particularly melting, transport and elasticity at high temperatures and pressures.