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This work presents the structural, morphological, and luminescent characterization of pure SrTiO3and SrTiO3:Eu3+powders doped with different europium atomic concentrations from 3.0 to 7.0 a.t.%. Those phosphors were prepared by pressure-assisted combustion synthesis using titanium oxide as precursor and were subjected to postannealing at 1200°C. XRD measurements indicated that undoped and Eu3+doped samples presented a single cubic crystalline phase and SEM images demonstrated that we have particles with sizes in the range of 0.2 µm–1.0 µm. Moreover, the size of the grains increases as the content of Eu3+dopant increases. A strong red emission from Eu3+ions was obtained by photoluminescence under excitation at 396 nm and confirmed by cathodoluminescence. All those results indicate that our red phosphors could be useful for potential applications in solid state lighting and field emission displays.

In this paper, the static optical transfer function of dielectric lithium niobate (LiNbO 3) electro-optic sensors is modeled and experimentally measured. This function represents the transmitted optical power at the output of an optical waveguide in a LiNbO 3 crystal which acts as an electric field sensor. The sensor is electrode-less and operates as a dielectric probe. Under such a condition, the electric field is present in the dielectric media surrounding the waveguide and the measured field intensity is determined by the boundary condition between the media and the LiNbO 3 crystal. The electro-optic transfer function is theoretically modeled and experimentally measured. Such a transfer function shows a sinusoidal shape, from which the half-wave electric field, the optical extinction ratio and the linear and nonlinear regions can be determined. LiNbO 3 electric field sensors are inherently wide band, and a sensing scheme is tested, showing a high-linearity sensing detection of high-intensity and wide-band electric fields.

Flexible graphene composites (FGCs) have been fabricated for heat dissipation purposes by using a mold-casting method. The flexible graphene composites have an elastic modulus of 18-68 MPa, which is suitable for flexible heat sinks in lighting applications. Scanning electron microscopy (SEM) images show that the graphene nanoplatelets in the FGCs coalesce in the through-plane direction, which enhances the thermal conductivity by increasing the inter-layer contact among the graphene nanoplatelets, and reduces the structural defects and grain boundaries. The heat dissipation properties of the FGCs were compared with devices for aluminum heat sinks (AHSs). For this, the operating temperature in the emitting area of a high-power UV-LED was measured as a function of the mass for each type of heat sink. Experiments on LEDs demonstrated that the FGCs with masses of 4.9 g and 5.5 g cooled down the hottest points on the LEDs at similar temperatures observed when the LED is operating on an AHS with 565 g of mass. The heat dissipation results demonstrated that the FGCs could be used as compact and lightweight heat sinks for high-power LEDs employed as lighting sources.

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