The apparatus is a selective radiation emitter to be used in conjunction with a photocell for thermophotovoltaic generation of electricity from heat. One embodiment of the emitter is a layer of selectively radiating rare earth oxide bonded onto a heated base metal layer by the use of an intermediate thin layer of porous metal powder. Another embodiment is an emitter of a thick metal powder layer combined with a rare earth oxide which is formed into the voids in the metal powder structure and bonded to a metal substrate which is to be heated. In this embodiment the metal powder grains are gold plated to limit their emissivity, so that emission outside the desired band of the rare earth oxide is greatly reduced.
A composite emitter (100) for a thermophotovoltaic cell and other applications, and a method of forming the composite emitter. The composite emitter includes a substrate (102) and a selective emitter layer (104) composed of at least one substantially pure ceramic oxide selective emitter material applied to the substrate using a thermal spraying method. The substrate is preferably made of a durable material such as a silicon-based material or a refractory metal oxide. In one embodiment, the selective emitter layer may be composed of two or more selective emitter materials. In another embodiment, the composite emitter may further include a reflective metal layer (106). The method includes providing a substrate and plasma spraying one or more selective emitter materials onto the substrate to a thickness of between about 10 microns and about 400 microns to form the selective emitter layer. Preferably, the selective emitter layer has an in situ density of between 80% and 95% of the bulk density of the selective emitter material used.
A rare earth optical temperature sensor is disclosed for measuring high temperatures. Optical temperature sensors exist that channel emissions from a sensor to a detector using a light pipe. The invention uses a rare earth emitter to transform the sensed thermal energy into a narrow band width optical signal that travels to a detector using a light pipe. An optical bandpass filter at the detector removes any noise signal outside of the band width of the signal from the emitter.
