Mechanical properties and machinability of GYGAG:Ce ceramic scintillators

Cerium doped gadolinium yttrium gallium aluminum garnet ceramics, GYGAG:Ce for short, have drawn a lot of attention and showed a very promising application in medical CT detectors. This mainly attributes to their excellent scintillation properties, such as high light output, low afterglow, fast decay and high x-ray stopping power. In order to provide more accurate lesion location in real CT diagnosis, ceramic scintillators need to be machined into regular pixelated arrays, and the pixels should well match with the photodiode elements. Therefore, in addition to the scintillation characteristics, the mechanical properties and machinability of these ceramic scintillators should have been studied further, but such data and references are limited. In this research, we focused on the mechanical properties and the machinability behaviour of GYGAG:Ce ceramics. It was observed that GYGAG:Ce ceramics with grain size around 8 mu m have the highest mechanical strength, and are highly suitable for machining process to achieve fine array pixels, for which a strict dimensional tolerance needs to be held

A far-red-emitting (Gd,Y)(3)(Ga,Al)(5)O-12:Mn2+ ceramic phosphor with enhanced thermal stability for plant cultivation

As for plants, far-red (FR) light with wavelength from 700 nm to 740 nm is critical for processes of photosynthesis and photomorphogenesis. Light-controlled development depends on light to control cell differentiation, structural and functional changes, and finally converge into the formation of tissues and organs. Phosphor converted FR emission under LED excitation is a cost-effective and high-efficient way to provide artificial FR light source. With the aim to develop an efficient FR phosphor that can promote the plant growth, a series of gadolinium yttrium gallium garnet (GYGAG) transparent ceramic phosphors co-doped with Mn2+ and Si4+ have been fabricated via chemical co-precipitation method, followed sintered in O-2 and hot isostatic pressing in this work. Under UV excitation, the phosphor exhibited two bright and broadband red emission spectra due to Mn2+: T-4(1) -> (6)A(1) spin-forbidden transition, and one of which located in the right FR region. And then, Ce3+ ions were co-doped as the activator to enhance the absorption at blue light region and the emission of Mn2+. It turns out that the emission band of GYGAG transparent ceramic phosphors matches well with the absorption band of phytochrome P-FR, which means they are promising to be applied in plant cultivation light-emitting diodes (LEDs) for modulating plant growth. Besides, the thermal stability of this material was investigated systematically, and an energy transferring model involves defects was also proposed to explain the phenomenon of abnormal temperature quenching

MEMS-based fabrication of high-performance inductors with back hollow structure and ferromagnetic film

International audienceThe development of novel on-chip device techniques is attracting more and more interest because of the increasing demand for communication electronics, wearable devices and Internet of Things (IoT) with features of low power consumption, high frequency-response, small size, fast transmission rate, and low-costs in the lab-on-chip field. This letter presents the high frequency performance enhancement of on-chip inductors by the use of a back hollow structure filled with CoFeB/ZnO/CoFeB thin ferromagnetic layers. The magnetization dynamic response of this ferromagnetic stacks deposited by RF-magnetron sputtering were investigated. The inductance increases by 41.2%–70.6% between 0.1 and 8 GHz reaching 70.6% at 6.9 GHz. Q-factor increases also in a range of 3% to 18% between 0.1 and 3.8 GHz and reach 18% at 1.5 GHz. The equivalent circuit model and simplified physical model of the individual inductor were established and used to model and describe the parameters of inductor, such as the inductance and Q-factor as function of frequency. The results show the potential for application of the back hollow structure inductors with ferromagnetic thin film in RF circuits