A5011667176- Ferroelectric and Piezoelectric Materials
- Microwave Dielectric Ceramics Synthesis
- Physics of Superconductivity and Magnetism
- Acoustic Wave Resonator Technologies
- Multiferroics and related materials
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Superconducting Materials and Applications
- Advanced Condensed Matter Physics
- Advanced ceramic materials synthesis
- Microwave Engineering and Waveguides
- Semiconductor materials and devices
- Gold and Silver Nanoparticles Synthesis and Applications
- Magnetic properties of thin films
- Atomic and Subatomic Physics Research
- Plasmonic and Surface Plasmon Research
- Copper Interconnects and Reliability
- ZnO doping and properties
- Antenna Design and Analysis
- Layered Double Hydroxides Synthesis and Applications
- Concrete and Cement Materials Research
- Microwave and Dielectric Measurement Techniques
- Superconductivity in MgB2 and Alloys
- Copper-based nanomaterials and applications
- Diamond and Carbon-based Materials Research
Imperial College London
2015-2025
Imperial Valley College
2023-2024
Weatherford College
2024
Northumbria University
2024
Physical Sciences (United States)
2024
London Centre for Nanotechnology
2012-2023
King's College London
2017
National Institute of Research and Development for Optoelectronics
2017
Washington State University
2017
Transnational Press London
2016
The real part of the permittivity (ε) and tan δ sintered alumina (Al 2 O 3 ) at about 9 GHz have been measured. dielectric properties examined as a function purity, pore volume, grain size. is found to depend very strongly on ε far less sensitive impurities dependence porosity can be described by simple mixture models expected. A model losses in single crystals cannot extended easily these materials where extrinsic factors such porosity, random crystal orientation, boundaries, microcracks,...
Studies of a BiFeO3 synthesis were performed to identify reasons for the appearance secondary phases, Bi25FeO39- and Bi2Fe4O9-type in reaction product. X-ray diffraction microstructural analyses, on samples with different concentrations impurities, showed that impurities starting material crucially influence phase composition A fraction generated phases strongly depends nature concentration impurities. The experimental results can be explained by theoretical consideration ternary relations...
Effective negative capacitance has been postulated in ferroelectrics because there is a hysteresis plots of polarization-electric field. Compelling experimental evidence effective presented here at room temperature engineered devices, where it stabilized by the presence paraelectric material. In future integrated circuits, incorporation such into MOSFET gate stacks would reduce subthreshold slope, enabling low power operation and reduced self-heating.
Using localized surface plasmon resonances (LSPR) to focus electromagnetic radiation the nanoscale shows promise of unprecedented capabilities in optoelectronic devices, medical treatments and chemistry, due a strong enhancement light-matter interactions. As we continue explore novel applications, require systematic quantitative method compare suitability across different geometries growing library materials. In this work, propose application-specific figures merit constructed from...
The dielectric loss (tan δ) of titanium dioxide (TiO 2 ) disks has been measured at a frequency 3 GHz. High‐purity TiO sintered to almost‐full density exhibits very high tan δ, which is interpreted be due oxygen deficiency. To counter this, doping with stable divalent and trivalent cations, such as Mg Al, leads low probably by preventing Ti 4+ reduction. δ polycrystalline doped ions ionic radii in the range 0.5–0.95 Å GHz can low: 6 × 10 −5 ( Q ∼ 17 000) temperature 300 K. undoped pure...
Low dielectric loss materials are required for applications in radio-frequency and microwave communications. Aluminium is the second most abundant element Earth’s crust aluminium oxide (alumina) one of commonest ceramics. Single crystals oxide, i.e., sapphire, possess lowest losses any material. Polycrystalline alumina has a higher due to extrinsic factors. The sintered studied an attempt determine causes loss. Impurities shown play important role, but microstructure also key factor....
A direct electrocaloric effect (ECE) measurement system, based on a modified-differential scanning calorimeter (DSC), allowing the acquisition of both thermal (ECE, heat capacity) and electrical (P-E loops, leakage current) information simultaneously, was used to analyze 〈001〉-oriented PbMg1/3Nb2/3O3-30PbTiO3 single crystals. Different electric-field-induced phase transitions were identified ECE measurements confirmed by dielectric measurements. The strongest (ΔTEC = 0.65 K) measured for an...
The complex permittivity and resistivity of float-zone high-resistivity silicon were measured at microwave frequencies for temperatures from 10 up to 400 K employing dielectric-resonator composite techniques.At below 25 K, where all free carriers are frozen out, loss-tangent values the order 2 4 measured, suggesting existence hopping conductivity or surface charge carrier in this temperature range.Use a dielectricresonator technique enabled measurement materials having higher dielectric...
Reducing loss in microwave dielectrics is critical to improving performance wireless communications systems. Grain boundaries polycrystalline dielectric ceramics have long been suspected of increasing loss. They are often cited as the main contributor observed difference losses between single crystals and ceramics. The exact configuration grain problematic quantify practice their influence on difficult distinguish from other defects such porosity, oxygen vacancies, impurities, dislocations....
The electrocaloric effects (ECEs) of the morphotropic phase boundary (MPB) composition 0.82(Na0.5Bi0.5)TiO3-0.18(K0.5Bi0.5)TiO3 (NBT-18KBT) are studied by direct measurements. maximum ECE ΔTmax = 0.73 K is measured at 160 °C under 22 kV/cm. This corresponds to an responsivity (ΔT/ΔE) 0.33 × 10−6 m/V, which comparable with best reported values for lead-free ceramics. A comparison between and indirect measurements shows significant discrepancies. measurement both positive negative effect...
This paper details the investigation of quality factor ( Q ), dielectric permittivity (ɛ r ) and temperature coefficient resonant frequency (τ f TE 01δ mode columbite binary niobate ceramics, with formula MNb 2 O 6 where M= 2+ cation, in relation to their degree sintering, microstructure phase composition. The ceramics were made from a mixed oxide preparative route fired over range temperatures 800° 1400°C, most formed structure. A comprehensive study was niobates containing transition metal...
Cerium oxide (CeO 2 ) has been prepared as a ceramic dielectric resonator by conventional solid-state route.The sintered CeO high quality factor (Q؋f), Q value of 10 000 at 6 GHz with relative permittivity () 23, and temperature coefficient resonant frequency ( f ؊53 ppm/°C.The increases to 20 when the is doped 1 mol% CaCO 3 .Higher levels doping lowers values simultaneously decreases .TiO slightly , but deceases value.The pure 105 5.58 it cooled 30 K, whereas Ϸ 85 5.48 for 1-mol%-CaCO -doped K.W. A.
A theory is suggested to explain the elasticity of particle assemblies. It shown that a regular cubic packing spheres has an effective Young’s modulus depends on contacts between individual particles. In particular, it noted interfacial attractive energy spheres, and thus provides direct method for measuring surface solids. However, most assemblies are neither nor regular. The problem describe properties these real systems in terms grains. Theoretically, powder compact should vary as fourth...
The highly anisotropic electrocaloric effect, evidenced by both direct measurements and a descriptive theoretical model in lead-free relaxor ferroelectric Sr0.75Ba0.25Nb2O6 single crystals, can be exploited producing low-cost grain-oriented ceramics. Combined with the broad-temperature-range cooling regime provided their polar nanoregions, these materials may key to future cost- energy-efficient solid-state refrigeration.