Monolithic oxide–metal composite thermoelectric generators (TEGs) were fabricated using multilayer co-fired ceramic technology. These devices consisted of Ni0.9Mo0.1 and La0.035Sr0.965TiO3 as p- and n-type thermoelectric materials, and Y0.03Zr0.97O2 was used as an insulator, sandwiched between p- and n-type layers. To co-fire dissimilar materials, p-type layers contained 20 wt. % La0.035Sr0.965TiO3; thus, these were oxide–metal composite layers. The fabricated device had 50 pairs of p–i–n junctions of 5.9 mm × 7.0 mm × 2.6 mm. The calculated maximum value of the electric power output from the device was 450 mW/cm2 at ΔT = 360 K. Furthermore, this device generated 100 μW at ΔT = 10 K and operated a radio frequency (RF) transmitter circuit module assumed to be a sensor network system.
Thin films of (Ba x Sr 1−x ) 1+y Ti 1−y and Zr, Gd codoped (Ba x Sr 1−x ) 1+y Ti 1−y were deposited on platinized sapphire substrates at 640 °C under constant flux of atomic oxygen or a mixture of atomic oxygen and nitrogen to synthesize perovskites of (Ba x Sr 1−x ) 1+y Ti 1−y O 3−δ (also referred to as BSTO), (Ba x Sr 1−x ) 1+y Ti 1−y O 3−z N z (also referred to as BSTON), and Zr, Gd codoped (Ba x Sr 1−x ) 1+y Ti 1−y O 3−z N z . Structural characterization was done via XRD and XPS, and electrical characterization was done via LCR (dielectric properties and tunability under DC bias) and P−E measurements. Although the levels of nitrogen incorporated within the perovskite structure appear to be very low as determined by XPS analysis, definite improvements in dielectric properties and tunability have been achieved by synthesis of the BSTON oxynitride films. For a composition of Ba 0.8 Sr 0.2 TiO 3−z N z an improvement by a factor of 1.72 for tunability and 1.44 for relative permittivity has been observed between the oxide and the oxynitride. The oxynitride achieved a tunability ratio of 6.78 to 1 (close to 7:1) under an applied electrical field of 34 kV/mm. The high throughput approach allowed us to highlight a compositional shift for the material with the best dielectric properties when comparing the oxide with the oxynitride thin films. Effects of codoping the perovskite structure with Zr and Gd have also been investigated and although the tunability and dielectric constant of the thin films were not improved, some improvements in dielectric losses were observed, along with a superparaelectric state as observed by P−E hysteresis measurements.
The 1.5 and 2.4 GHz range 5IDT-type longitudinally coupled surface acoustic wave (SAW) resonator filters have been developed using ZnO/sapphire substrate. The 1.5 GHz range SAW filter has the minimum insertion loss of 1.0 dB and the relative bandwidth of 2.4% at the insertion loss of 3 dB.
The 2.4 GHz range SAW filter has the minimum insertion loss of 1.7 dB and the relative bandwidth of 1.7% at the insertion loss of 3 dB.
These filters are suitable for use as RF-stage filters in a personal digital cellular (PDC) system terminal and a wireless local area network (LAN) adapter, respectively.
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