NSUF 11-322: Irradiation damage of Ba(Zn1/3Ta2/3)O3 ceramic materials
Development of high dielectric-constant material with diminished microwave loss and a near-zero temperature coefficient of resonant frequency, will enable the production of smaller and higher performance microwave devices that can operate over a wider range of frequencies. The project is intended to develop a fundamental understanding of the microscopic mechanism that causes loss in practical dielectric materials, and explain why some materials exhibit better microwave performance than others. It will also systematically investigate the resilience of this materials performance to high energy irradiation doses to determine if it can be used in "radiation hard" appplications. The nature of performance enhancing and degrading defects temperature-compensated Ba(Zn1/3Ta2/3)03 ceramics will be investigated. Our recent work using ab-initio electronic structure calculations were able to elucidate the physical reason for the unusually low loss tangent in materials with a large dielectric constant. Typically ionic materials with large polarizable atoms also are weakly bonded and are particularly susceptible to anharmonic phonon absorption. The presence of significant charge transfer between the cation d-orbitals provides a degree of covalent directional bonding between atoms that resist angular distortions, a property absent in conventional ionic compounds. Charge is transferred from Ta 5d-levels in the conduction band (empty states at and near the CBM) to Zn –3d levels (full states at and near the VBM). The d-electron bonding in BZT and BCT is responsible for producing a more rigid lattice with higher melting points, enhanced phonon energies than comparable ionic materials and thus inherently low microwave loss. To better understand the role of extrinsic factors in the performance of practical microwave dielectrics, we correlate the intrinsic and extrinsic electronic properties with the microwave loss tangent of material with a wide range of defect concentrations. Neutron irradiation will be used to systematically introduce defects in the materials and the loss tangent, as well as the nature and concentration of defects will be determined using a range of electrical, optical and magnetic probes. Predictions by density functional theory of the harmonic and anharmonic phonon spectra for defect-free and defective crystals will be directly compared to the experimental results. This will allow us to determine the influence of defects on the physical properties and extend our understanding of the role of phonons in microwave loss. Preliminary neutron damage studies at INL from a number of years ago indicate that neutron fluxes of above 10^13/cm^2 are appropriate for these experiments. This project will be carried out from 4/2011 to 4/2012 and is funded by the Army Research Office and discretionary funds at Arizona State University
Additional Info
| Field | Value |
|---|---|
| Abstract | Development of high dielectric-constant material with diminished microwave loss and a near-zero temperature coefficient of resonant frequency, will enable the production of smaller and higher performance microwave devices that can operate over a wider range of frequencies. The project is intended to develop a fundamental understanding of the microscopic mechanism that causes loss in practical dielectric materials, and explain why some materials exhibit better microwave performance than others. It will also systematically investigate the resilience of this materials performance to high energy irradiation doses to determine if it can be used in "radiation hard" appplications. The nature of performance enhancing and degrading defects temperature-compensated Ba(Zn1/3Ta2/3)03 ceramics will be investigated. Our recent work using ab-initio electronic structure calculations were able to elucidate the physical reason for the unusually low loss tangent in materials with a large dielectric constant. Typically ionic materials with large polarizable atoms also are weakly bonded and are particularly susceptible to anharmonic phonon absorption. The presence of significant charge transfer between the cation d-orbitals provides a degree of covalent directional bonding between atoms that resist angular distortions, a property absent in conventional ionic compounds. Charge is transferred from Ta 5d-levels in the conduction band (empty states at and near the CBM) to Zn –3d levels (full states at and near the VBM). The d-electron bonding in BZT and BCT is responsible for producing a more rigid lattice with higher melting points, enhanced phonon energies than comparable ionic materials and thus inherently low microwave loss. To better understand the role of extrinsic factors in the performance of practical microwave dielectrics, we correlate the intrinsic and extrinsic electronic properties with the microwave loss tangent of material with a wide range of defect concentrations. Neutron irradiation will be used to systematically introduce defects in the materials and the loss tangent, as well as the nature and concentration of defects will be determined using a range of electrical, optical and magnetic probes. Predictions by density functional theory of the harmonic and anharmonic phonon spectra for defect-free and defective crystals will be directly compared to the experimental results. This will allow us to determine the influence of defects on the physical properties and extend our understanding of the role of phonons in microwave loss. Preliminary neutron damage studies at INL from a number of years ago indicate that neutron fluxes of above 10^13/cm^2 are appropriate for these experiments. This project will be carried out from 4/2011 to 4/2012 and is funded by the Army Research Office and discretionary funds at Arizona State University |
| Award Announced Date | 2011-08-30T00:00:00 |
| Awarded Institution | Idaho National Laboratory |
| Facility | Advanced Test Reactor |
| Facility Tech Lead | Alina Zackrone, Ayman Hawari , Yaqiao Wu |
| Irradiation Facility | None |
| PI | Nathan Newman |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 322 |