High Temperature Solid State Diffusion Research Articles

Luminescence investigation of red emitting CaAlSiO4F: Eu3+ doped phosphor for white LEDs based on oxyfluoride matrix

A series of Eu3+-doped of CaAlSiO4F red-emitting phosphors for different concentrations were successfully synthesized by using high temperature solid state diffusion method. The phase identification of the prepared phosphor was recorded using x-ray diffraction (XRD). In PL study, the emission peak of prepared phosphor was located at 595 nm and 618 nm due to 5D0 → 7F1 and 5D0 → 7F2 transitions at excitation of 257 nm, 395 nm and 465 nm. Morphological behaviour of prepared sample was analyzed by using scanning electron microscope (SEM). Commission de l'Eclairage chromaticity (CIE) coordinates were analyzed based on the PL emission spectra of the series CaAlSiO4F: Eu3+ activated phosphor. Therefore, these possible outcomes indicate that the CaAlSiO4F: Eu3+ products have great potential applications in solid state lighting industry.

Molten salt-assisted synthesis of carbo-nitride TiC0.5N0.5 and MAX phases Ti2AlC0.5N0.5 and Ti3AlCN at low temperature under different atmospheres

Transition metal-based carbo-nitride solid solution phases have wide application in electrical, electronic, automotive, and refractory industries due to the excellent combination of metallic and ceramic properties. Mainly, carbo-nitride phases were synthesized by high-temperature solid-state diffusion, carbothermal reduction-nitridation, HIP, SHS, pressureless sintering at high temperature, etc. All the methods required considerable investment and production costs, limiting their application in the larger area of research. To overcome all the problems related to the synthesis, one simple, cost-effective, energy-efficient, and environmentally friendly method is required where synthesis will be carried out at a lower temperature with a shorter soaking time. Molten salt-assisted synthesis method fulfils these requirements by accelerating the diffusion rate for phase formation through a chemically inert liquid medium. In this manuscript, carbo-nitride TiC0.5N0.5 and MAX phases Ti2AlC0.5N0.5 and Ti3AlCN have been synthesized using this method with a different atmosphere (Ar, N2, and Air) at a relatively lower temperature with a shorter period of time and characterized by XRD, SEM, particle size analyzer, and HRTEM. The relative density was measured by Archimedes’ principle in case of all the samples and electrical conductivity of the respective samples was determined by the four-probe method.

Improved stability and efficiency of perovskite via a simple solid diffusion method

CsPbBr3 perovskite quantum dots (QDs) have excellent properties such as high emission quantum yield, adjustable spectrum, and wide color range. They have potential prospects in light-emitting diode (LED) displays and solar cells. However, CsPbBr3 QDs suffer from a low stability with a high sensitivity to water, heat, and light. Here, for the first time, we report a simple method to improve their stability using a high-temperature solid state diffusion to synthesize highly stable and high-quality CsPbBr3 QDs in a small pore size LTA zeolite (0.41 nm). First, the mixture of PbBr2, CsBr and LTA zeolite was heated at 650 °C, and the raw materials PbBr2 and CsBr were diffused into the LTA zeolite through a small aperture. Then, the CsBr/PbBr2 in the composite was reassembled into CsPbBr3 QDs (CsPbBr3@LTA) at room temperature. The CsPbBr3@LTA obtained by this synthesis method have a high photoluminescence quantum yield (PLQY ∼66%) and extremely high stability. The PLQY of CsPbBr3@LTA remained above 66% after being kept in the air for 17 months. The PL intensity of CsPbBr3@LTA remained 78% of the initial value after being immersed in water for 554 days and the PL intensity changed insignificantly after laser irradiation for 20 days.

Microjoining developments of ASS316L/AZ31 TLP bonds using Cu and Ni high temperature solid state diffusion

Dissimilar joining of austenitic stainless steels to magnesium alloys has recently attained significant attention for the reasons of decreasing the environmental impacts by reducing vehicles emissions and minimizing fuel consumption while maintaining the requireddesign level of mechanical characteristics. This research work is directed toward microscale joining enhancement of the 316 L/(Cu or Ni foils) solid interface through the formation of reaction layers through high temperature solid-state diffusion at 900oC for 15min. Afterward, transient liquid phase bonding (TLP) with AZ31 took place at 530oC and 510oC for 20min using Cu and Ni foils, respectively. The scanning electron microscopy analyses revealed formation of metallurgical micro-reaction films between 316L steel and either Cu or Ni interlayers. Formation of these films enhanced the subsequent TLP bonding with the magnesium alloy AZ31. High temperature solid state interlayer diffusion increases the joint shear strength by 30% when using Cu interlayer and 67% when using Ni interlayer relative to those obtained without the high temperature solid state diffusion stage.

Synthesis and photoluminescence properties of Eu doped LiBaPO4 phosphors for solid state lighting

Phosphor LiBaPO4: Eu3+ was successfully synthesized by Pechini (citrate gel) method which is more efficient than conventional high temperature solid state diffusion reaction. X-ray diffraction analysis confirmed the single phase formation of LiBaPO4 with hexagonal crystal structure. Luminescence results showed that the phosphor could be efficiently excited by near UV with intense excitation peak at 393 nm and exhibited two bright red emission narrow bands. In the wavelength range 575–640 nm these bands are centered at 595 and 615 nm, corresponding to characteristics transitions 5D0→7F1 and 5D0→7F2 respectively of Eu3+, with maximum intensity peak at 615 nm. When Eu3+ in LiBaPO4:Eu3+ was reduced by the carbo-thermal reduction process to Eu2+ intense blue broad emission band centered at 472 nm was obtained for LiBaPO4:Eu2+ phosphor when monitored at 350 nm. Hence both of phosphors could be use in solid state lighting application for fabrication of white light emitting diodes.

High pressure synthesis of BN and BCN crystals and their functionalization

Hexagonal BN (hBN) and cubic BN (cBN) are known as the representative crystal structures of BN. The former is chemically and thermally stable, and has been widely used as an electrical insulator and heat-resistant materials. The latter, which is a high-density phase, is an ultra-hard material second only to diamond. Recently, some progresses in the synthesis of high purity BN crystals were achieved by using Ba-BN as a solvent material at high pressure crystal growth [1]. Band-edge natures (cBN Eg=6.2eV and hBN Eg=6eV) were characterized by their optical properties. The key issue to obtain high purity crystals is to reduce oxygen and carbon contamination in the growth circumstances. It should be emphasized that hBN exhibits attractive potential for deep ultraviolet (DUV) light emitter [2 ] and also superior properties as substrate of graphene devices [3]. In this study, the effect of carbon impurity in BN is investigated. Three types of experimental approaches were carried out; (1) synthesis of high purity hBN single crystals and its characterization with respect to residual carbon, (2) high temperature solid state diffusion of carbon into hBN and its characterization, and (3) high temperature annealing of turbostratic B-C-N(t-BCN) compound under high pressure. t-BCN flakes obtained by chemical vapour deposition process was annealed near 3000C and 2GPa so as to become well crystallized.At annealing near 3000C at 2GPa with graphite, carbon incorporation of 1E21/cm3 in hBN was achieved with exhibiting totally different Cathode Luminescence spectra feature with high purity hBN crystals. Since major carbon contribution may affect the crystal structure of the 2-D layers stacking in hBN system, phase stability of BCN ternary phase will be introduced by the experimental results of high temperature annealing. Furthermore, effect of carbon impurity upon the synthesis of wurtzite BN from highly crystalline hBN via martensitic phase transformation will also be introduced.

Mechanoluminescence and lyoluminescence characterization of Li2BaP2O7:Eu phosphor

In this work mechanoluminescence and lyoluminescence properties of Li2BaP2O7: Eu phosphor are reported. Phosphor was synthesized through high temperature solid state diffusion method. Analysis of phosphor was made through various characterization techniques such as mechanoluminescence (ML), lyoluminescence (LL), x-ray powder diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL). It was observed that ML intensity showed good enhancement with variation in time, concentration of dopant Eu, mass of piston and impact velocity. Lyoluminescence intensity was also found to increase with change in time and mass of the sample. Variation in gamma doses imparted to Li2BaP2O7: Eu phosphor was observed to affect both the ML and LL intensities' respectively. Both the ML and LL intensity attain a maximum value Im at a particular time tm but afterwards, it decreases and finally disappears. Morphology of Li2BaP2O7: Eu luminescent material was also studied using scanning electron microscope technique. The average particle size in Eu doped lithium barium diphosphate phosphor was around 2 μm.

Thermoluminescence dosimetric characteristics of thulium doped ZnB2O4 phosphor

Polycrystalline powder samples of rare earth doped Zinc borates were synthesized by high temperature solid state diffusion technique. Dosimetric characteristics of the phosphor like thermoluminescence glow curve, TL emission spectra, dose–response, fading studies, reproducibility and reusability studies were carried out on the synthesized phosphors. Among the different rare earth doped phosphors, thulium doped zinc borate was found to have a higher sensitivity. Hence detailed dosimetric characteristics of this phosphor were carried out. It is observed that the dose–response is linear from 10mGy to 103Gy in this phosphor. EPR measurements were carried out on unirradiated, gamma irradiated and annealed phosphors to identify the defect centers responsible for thermoluminescence. A TL model is proposed based on the EPR studies in these materials. Kinetic parameters were evaluated for the dosimetric peaks using various methods. The experimental results show that this phosphor can have potential applications in radiation dosimetry applications.

Thermoluminescence properties of rare earth doped lithium magnesium borate phosphors

This paper reports the thermoluminescence (TL) properties of rare earth doped lithium magnesium borate (LMB) polycrystalline phosphor. LMB phosphor has been prepared by high temperature solid state diffusion method. Among all the rare earth doped LMB phosphors, terbium doped material has shown maximum TL sensitivity with a broad dosimetric glow peak at 240 °C. near the tissue equivalent TL phosphor with terbium dopant has about four times the TL sensitivity of TLD-100. The main dosimetric properties such as glow curve stability, TL response versus absorbed dose, post-irradiation storage stability, and reusability are investigated. This TL material has a linear dose response up to 10 3 Gy, negligible storage fading and a simple annealing procedure for reuse. The TL emission spectra of LMB:Tb 3+ showed broad green emission at 544 nm, which merged with host emission. The characteristic Tb 3+ emissions are seen in the photoluminescence (PL) spectra.

Dosimetric properties of rare earth doped LiCaBO 3 thermoluminescence phosphors

Lithium Calcium borate (LiCaBO 3) polycrystalline thermoluminescence (TL) phosphor doped with rare earth (RE 3+) elements has been synthesized by high temperature solid state diffusion reaction. The reaction has produced a very stable crystalline LiCaBO 3:RE 3+ phosphors. Among these RE 3+ doped phosphors thulium doped material showed maximum TL sensitivity with favorable glow curve shape. TL glow curve of gamma irradiated LiCaBO 3:Tm 3+ samples had shown two major well-separated glow peaks at 230 and 430 °C. The glow peak at 430 °C is almost thrice the intensity of the glow peak at 230 °C. The TL sensitivity of the phosphor to gamma radiation was about eight times that of TLD-100 (LiF). Photoluminescence and TL emission spectra showed the characteristic Tm 3+ peaks. TL response to gamma radiation dose was linear up to 10 3 Gy. Post-irradiation TL fading on storage in room temperature and elevated temperatures was studied in LiCaBO 3:Tm 3+ phosphor.

Production of oriented two-phase bicrystals by a diffusion bonding technique

An experimental technique is presented for high temperature solid state diffusion bonding of two different crystals. The relative orientation of the crystals and the orientation of the boundary plane can be chosen arbitrarily. Unwanted recrystallization close to the boundary plane is avoided by precise adjustment of the applied bonding force. Special care is taken for preparation of the contact surfaces of the two crystals, to suppress as far as possible superficial straining and planarity defects on macroscopic and microscopic scales. This technique is of use for any stable two-phase system at thermal equilibrium, and has been applied successfully to obtain Al/Al 2Cu and Ag/Cu two-phase bicrystals. With both systems, a one hundred hour high temperature treatment is sufficient to produce interfaces free from embritteling porosites, on areas large enough to allow cutting of specimen for macroscopic mechanical tests. These experimental results and the kinetics of bonding are discussed and compared to the theoretical model proposed by Garmong, Paton and Argon (1975).