Investigation of Solution-Processed Ga2O3 Thin Films and their Application in Dielectric Materials

In this paper, polycrystal Ga2O3 thin films were grown on crystal n+-Si substrates by solution process. The XRD profile revealed that monoclinic β-Ga2O3 and rhombohedral α-Ga2O3 were coexisting in the film. The solution-process Ga2O3 film exhibited an ultrahigh transmittance (>97%) to a wavelength range of 280 nm~800 nm. The optical bandgap of ~5.0 eV and breakdown field of 4.2 MV/cm of the Ga2O3 thin film was obtained. Dielectric parameters such as capacitance, dielectric permittivity and loss tangent were investigated. It was observed that these parameters have a strong dependence on frequency.

Paving the Way to Eco-Friendly IoT Antennas: Tencel-Based Ultra-Thin Compact Monopole and Its Applications to ZigBee

An ultrathin, compact ecofriendly antenna suitable for IoT applications around 2.45 GHz is achieved as a result of exploring the use of Tencel fabric for the antenna’s design. The botanical ecofriendly Tencel is electromagnetically characterized, in terms of relative dielectric permittivity and loss tangent, in the target IoT frequency band. To explore the suitability of the Tencel, a comparison is conducted with conventionally used RO3003, with similar relative dielectric permittivity, regarding the antenna dimensions and performance. In addition, the antenna robustness under bent conditions is also analyzed by measurement. To assess the relevance of this contribution, the ultrathin ecofriendly Tencel-based antenna is compared with recently published antennas for IoT in the same band and also, with commercial half-wave dipole by performing a range test on a ZigBee-based IoT testbed.

Dielectric Properties of Polyester Reinforced with Carbon Black Particles

Dielectric constant and ac conductivity of Polyester doped with carbon black are investigated in the frequency range (0.5-103) KHz and within the temperature range (26-80) oC. Dielectric permittivity and loss tangent reduced with increasing frequency and increase with increasing temperature. The ac conductivity σac for all samples were found to be weak frequency dependent at low frequency, however vary with frequency as a power law ωs at higher frequency range. The variation of frequency exponential factor s between 0.63 and 0.77, indicates a dominant hopping process at low temperatures. From the temperature dependence of dc conductivity, the increase of activation energy was observed with carbon black concentrations.

Dielectric Properties and Diffuse Phase Transition of Sol-Gel Derived 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 Ceramics

The 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (abbreviated to BNT-BT) powder and ceramic was synthesized by sol-gel process. The phase structure and dielectric properties of the ceramics were investigated. The ceramic was sintering at 1000-1100 degree C for 2-4 h in air atmosphere, and the X-ray diffraction (XRD) results revealed that the samples was pure perovskite-type phase. The Curite temperature of BNT-BT ceramics was high up to 348 degree C. The temperature dependence of dielectric permittivity and loss revealed there were two phase transitions, which were from ferroelectric (tetragonal) to anti-ferroelectric (rhombohedral) and anti-ferroelectric to paraelectric (cubic) in BNT-BT ceramics. Diffuse phase transitions were observed in BNT and BNT-BT ceramics and the Curie-Weiss Exponent (CWE) were nearly 2.

Dielectric relaxation and microwave loss in the La(Mg1/2Ti1/2)O3–(Na1/2Bi1/2)TiO3 perovskite ceramics

Dielectric response of the perovskite ceramics (1–x)La(Mg1/2Ti1/2)O3–x(Na1/2Bi1/2)TiO3 [(1–x)LMT–xNBT] (0 ⩽ x ⩽ 0.6) has been characterized at radio, microwave, and far infrared frequency ranges. Temperature variations of the dielectric permittivity and loss estimated by different methods were compared and analyzed. It was revealed that the low temperature dielectric response of the compositions with x ⩾ 0.2 is frequency-dependent over a wide range (102–109 Hz) below the resonant frequencies of the polar phonon modes. Contributions of different factors (both extrinsic and intrinsic) to the microwave dielectric loss of the ceramics were considered. The dielectric relaxation has been associated with the amount of bismuth in the system. The relaxation in LMT–NBT was considered in the context of similar effects observed in other Bi-containing, A-site disordered oxygen-octahedral compositions.