Fabrication of barium titanate (BaTiO 3 ) specimens was accomplished with binder jetting additive manufacturing, and build parameters (e.g. binder saturation and layer thickness) and sintering profiles were modified to optimize the density achieved and the crystal structures obtained in the 3D printed parts. Surface and cross sectional grain morphology was characterized by scanning electron microscopy (SEM) revealing grain growth on localized areas of BTO fabricated specimens after sintering. Crystal structure was analyzed by X-ray diffraction (XRD) where the presence of a hexagonal phase was observed for 2 BaTiO 3 only when sintered at 1400ºC. The dielectric constant of the fabricated BaTiO 3 specimens sintered at 1260ºC was obtained by using a K u -band wave-guide and vector network analyzer setup in which the relative permittivity was measured from 8.6 to 6.23 for a frequency range of 12.4 to 18 GHz, respectively. When sintered at 1400ºC for 4 hours, a density of 3.93 g/cm 3 was obtained, which corresponds to 65.2% of the theoretical density.Piezoelectric properties exhibited a d 33 value of 74.1 for specimens also sintered at 1400ºC.Results reported in this paper demonstrate the feasibility of BTO as a binder jetting material for 3D printed dielectric structures, ceramic capacitors and gas and pressure sensors.

Wireless passive temperature sensors are receiving increasing attention due to the ever-growing need of improving energy efficient and precise monitoring of temperature in high temperature energy conversion systems such as gas turbines and coal-based power plants. Unfortunately, the harsh environment such as high temperature and corrosive atmosphere present in these systems has significantly limited the reliability and increased the costs of current solutions. Therefore, this paper presents the concept and design of a low cost, passive, and wireless temperature sensor that can withstand high temperature and harsh environments. The temperature sensor was designed following the principle of metamaterials by utilizing Closed Ring Resonators (CRR) in a dielectric ceramic matrix. The proposed wireless, passive temperature sensor behaves like an LC circuit, which has a temperature dependent resonance frequency. Full wave electromagnetic solver Ansys Ansoft HFSS was used to validate the model and evaluate the effect of different geometry and combination of Split Ring Resonator (SRR) structures on the sensitivity and electrical sizes of the proposed sensor. The results demonstrate the feasibility of the sensor and provide guidance for future fabrication and testing.

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This paper presents the fabrication, modeling, and testing of a metamaterial based passive wireless temperature sensor consisting of an array of closed ring resonators (CRRs) embedded in a dielectric material matrix. A mixture of 70 vol% Boron Nitride (BN) and 30 vol% Barium Titanate (BTO) is used as the dielectric matrix and copper washers are used as CRRs. Conventional powder compression is used for the sensor fabrication. The feasibility of wireless temperature sensing is demonstrated up to 200 C. The resonance frequency of the sensor decreases from 11.93 GHz at room temperature to 11.85 GHz at 200 C, providing a sensitivity of 0.462 MHz C. The repeatability of temperature sensing tests is carried out to quantify the repeatability. The highest standard deviation observed is 0.012 GHz at 200 C.

Enhancing the performance of dielectric capacitors toward higher energy density and higher operating temperatures has been drawing increased interest. Therefore, in this investigation, research efforts were dedicated to the fabrication and characterization of nanocomposites in order to enhance the energy density at both room temperature and elevated temperature. The dielectric capacitors are fabricated using nanocomposites composed of BaTiO3 nanoparticles with polyimide (PI) matrix aiming at combining the high relative dielectric permittivity of the ceramic filler and the high breakdown strength of the polymeric matrix. Dielectric energy storage performance is assessed for nanocomposites with volume fractions ranging from 0 to 20% under operating frequency from 20 Hz to 1 MHz and temperatures ranging from 20 to 120∘C. It is observed that with the increase of temperature, the capacitance increased while the energy density slightly decreased but significantly higher than pure polymer samples. The highest energy density was found for BaTiO3/PI nanocomposites with 20% volume fraction, 9.63 J/cm3 at 20∘C and 6.79 J/cm3 at 120∘C. Overall, testing results indicate that using nanocomposites of BaTiO3/PI as a dielectric component shows promise for implementation to preserve high energy density values up to temperatures of 120∘C.