Scintillation properties of Tm-doped Lu3Al5O12 single crystals

Using the micro-pulling-down (μ-PD) method, Tm-doped Lu₃Al₅O₁₂ (Tm:LuAG) single crystals were grown to examine their scintillation properties. In transmittance spectra, they exhibited about 80% transparency in the wavelengths longer than 320 nm and five absorption lines due to Tm³⁺ 4f–4f transitions were observed. ²⁴¹Am α-ray excited radioluminescence spectra were measured and intense 4f–4f emission peaks were observed with the host emission. When excited by ¹³⁷Cs γ-Ray to obtain pulse height spectra, Tm 1% doped LuAG showed the highest light yield coupled with a photomultiplier (PMT) or a silicon avalanche photodiode (Si-APD). The light yield was estimated to be 5800 and 7300 photons/MeV for PMT and Si-APD, respectively. Decay time profiles consist of two exponential components and the fast and slow components are considered to be attributed to the host and the combination of the host and Tm³⁺ 4f–4f emission, respectively.     

Crystal growth and scintillation properties of Nd-doped Lu3Al5O12 single crystals with different Nd concentrations

Nd 0.1%, 0.5%, 1% and 3% doped Lu₃Al₅O₁₂ (Nd:LuAG) single crystals were grown in the nitrogen atmosphere by the micro-pulling down (μ-PD) method. The grown crystals had a single-phase confirmed by powder XRD analysis. In absorption spectra, some weak absorption lines due to Nd³⁺ 4f-4f transitions were observed and their intensity increased with the increase of Nd concentration. When excited by ²⁴¹Am α-ray, a broad emission peak due to defects in the host lattice at 320 nm and some sharp lines due to Nd³⁺ 4f-4f transitions at wavelength longer than 400 nm were observed. The decay time profiles of Nd:LuAG under γ-ray excitation were well approximated by two exponential function of 340-760 ns and 3-5 μs for each sample. By pulse height measurement using ¹³⁷Cs, Nd 0.5%:LuAG showed the highest light yield of 7600 ± 760 photons/MeV.     

Fiber Single-Crystal Growth from the Melt for Optical Applications

The micro-pulling-down technique has been applied to produce undoped and 0.1% Nd³⁺-doped Y₃Al₅O₁₂ garnet single-crystal fibers with controlled diameter. The hot zone construction and fiber-pulling conditions have been optimized. As a result, growth of transparent and homogeneous fiber crystals has been achieved. The crystals have been grown under 10⁵ Pa (1 atm) of argon atmosphere, with the pulling rate varied in the range of 0.3–2.0 mm/min. One hundred percent of the starting melt has been normally transformed into a crystalline material, with an empty crucible ready for the next growth procedure. The as-produced fibers demonstrate promising optical properties.     

Liquid phase epitaxy of films with langasite structure

Epitaxial films of Na₂CaGe₆O₁₄ with langasite structure were deposited by liquid phase epitaxy (LPE) technique on isomorphic Nd₃Ga₅SiO₁₄ substrates at a growth temperature of about 1000°C using K₂O–V₂O₅ based flux. The films were about 100 μm in thickness and had rough surface morphology. The film composition measurements were made by scanning electron-probe microanalysis (EPMA). EPMA data indicated low content of flux forming K⁺ and V⁵⁺ cations in the films grown. Ca²⁺ enrichment and Na⁺ decrease were detected in the vicinity of film/substrate interfaces.     

Crystal growth and scintillation properties of Er-doped Lu3Al5O12 single crystals

Er-doped Lu₃Al₅O₁₂ (Er:LuAG) single crystalline scintillators with different Er concentrations of 0.1, 0.5, 1, and 3% were grown by the micro-pulling-down (μ-PD) method. The grown crystals were composed of single-phase material, as demonstrated by powder X-ray diffraction (XRD). The radioluminescence spectra measured under ²⁴¹Am α-ray excitation indicated host emission at approximately 350 nm and Er³⁺ 4f-4f emissions. According to the pulse height spectra recorded under γ-ray irradiation, the 0.5% Er:LuAG exhibited the highest peak channel among the samples. The γ-ray excited decay time profiles were well fitted by the two-component exponential approximation (0.8 μs and 6-10 μs).     

Eu-doped LiF-SrF2 eutectic scintillators for neutron detection

Eu²⁺ 0.05%, 0.1%, and 0.2% activated LiF-SrF₂ eutectic scintillators were prepared by the Bridgman method using ⁶Li enriched (95%) raw material. The α-ray-induced radio luminescence spectra showed intense emission peak at 430 nm due to an emission from Eu²⁺ 5d-4f transition in the Eu:SrF₂ layers. When excited by ²⁵²Cf neutrons, all the samples exhibited almost the same light yields of 5000-7000 ph/n with a typical decay times of several hundreds ns.     

Crystal growth and scintillation properties of Ce-doped sodium calcium lutetium complex fluoride

0.1%, 0.5%, 1% and 3% Ce doped scintillation crystals based on NaF-CaF₂-LuF₃ solid solutions were grown from the melt using Micro-Pulling-Down (μ-PD) method. The grown crystals were transparent and their transmittance was approximately 80% for the wavelengths longer than 320 nm. Concerning the scintillation properties, radio-luminescence peaks of the crystals were detected at approximately 330 nm. The light yield of the crystals was also measured using γ-ray (¹³⁷Cs and ²²Na) as the excitation source.     

Carbon nanotubes based strain sensors

This paper presents the design, fabrication and experimental results of carbon nanotubes (CNTs) based strain sensors. The sensors were fabricated by pressed CNTs tablets and elastic polymer beam. The diameter of multiwalled nanotubes (MWNTs) varied between 10 and 30 nm. The tablets of multiwalled CNTs having nominal thickness of 1.0 mm were pressed at a pressure of 200 and 300 MPa. The inter-electrodes distance (length) and width of the surface-type samples were in the range of 10–12 mm and 5–6 mm respectively. The DC resistance of the sensors having the strain sensitivity in the range of 50–80 in average increased under tension and decreased under compression.     

Humidity sensing properties of Cu2O-PEPC nanocomposite films

In this study, the blend of copper oxide nanopowder (Cu2O), 3 wt.% and poly-N-epoxypropylcarbazole (PEPC), 2 wt.% in benzol were drop-casted on glass substrates with pre-deposited surface-type silver electrodes for the fabrication of Cu2O-PEPC nanocomposite thin films. The thicknesses of the Cu2O-PEPC films were in the range of 10-13 μm. The effect of humidity on the electrical properties of the nanocomposite films was investigated by measurement of the capacitance and dissipation of the samples at two different frequencies of the applied voltage: 120 Hz and 1 kHz. The AC resistance of the samples was determined from values of dissipation. The DC resistance was measured directly. The effect of ageing on the humidity sensing properties of the nanocomposite was observed. After the ageing it was observed that at 120 Hz and 1 kHz, under humidity of up to 86% RH , the capacitance of the cell increased by 85 and 8 times and resistance decreased by 345 and 157 times, accordingly, with respect to 30% RH conditions. It was found that with increase of the frequency, the capacitance and resistance of the samples decreased. It is assumed that the humidity response of the cell is associated with diffusion of water vapors and doping of the semiconductor nanocomposite by water molecules.