Effect of sintering temperature on the growth of (K0.5Na0.5)NbO3 single crystals fabricated by the solid-state crystal growth method

The effect of sintering temperature on the growth of (K0.5Na0.5)NbO3 (KNN) single crystals fabricated by a solid-state crystal growth method with a sintering aid of 2 wt%Co3O4 and the seed crystals of (110) and (100) KTaO3 was investigated. For the KNN single crystals fabricated with the (110) KTaO3 seed crystal, crystal growth length was gradually increased with increasing sintering temperature at the temperatures of 1020 °C–1120 °C. At the temperatures of 1130 °C–1200 °C, rapid growth was observed and a grown single crystal reached the surfaces of the ceramic compact containing the seed crystal. The length of the KNN crystal sintered at 1140 °C for 24 h was 690 μm. On the other hand, such rapid growth was not observed for the KNN single crystals fabricated with the (100) KTaO3 seed crystal. The length of the KNN crystal sintered at 1140 °C for 24 h was 160 μm. The dielectric, ferroelectric, and piezoelectric properties of the KNN single crystal fabricated with the (110) KTaO3 seed crystal at a sintering temperature of 1140 °C were reported.

Source:IOPscience


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Synthesis and optical characterization of Nickel doped Thiourea Barium Chloride (TBC) single crystals

Organometallic Thiourea barium chloride (TBC) single crystals were synthesized using solution evaporation process at room temperature. Synthesized thiourea barium chloride crystals were recrystallized and during the recrystallization process 1M%, 2M% and 5M% of nickel (Ni) was added to the solution and kept for crystallization. The variation of intensity peaks and the shift in the XRD peaks were observed due to the incorporation of nickel in the host matrix. Variations in the absorbance and transmittance spectra of the pure and Ni doped crystals further confirms the presence of nickel in TBC single crystal. The optical bandgap of the pure and nickel doped single crystals were calculated using Touc's relation. The results show that bandgap decreased with the dopant concentration in the thiourea barium chloride crystal. The optical constants such as extinction coefficient and reflectance were also studied using the absorption spectrum. The FTIR absorption also shows minute shift in the absorption peaks due to the presence of nickel in the host matrix. Photoluminescence spectra of pure and doped crystals were studied.

Source:IOPscience
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Distributed Feedback Laser Based on Single Crystal Perovskite

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry–Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Source:IOPscience

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Heavy ion induced luminescence studies of YAlO3:Tb3+, Tm3+ single crystals

Ionoluminescence (IL), photoluminescence (PL) and thermoluminescence (TL) studies of YAlO3:Tb3+, Tm3+ (1 at %) single crystals are carried out using 100 MeV Si7+ ions for the fluence 3.91 × 1012 ions cm−2. IL peaks are recorded in the range 385–450, 493, 544, 585 and 624 nm in Tb3+- and 353, 459, 523, 651 and 763 nm in Tm3+-doped YAlO3 single crystals, respectively. PL studies also show similar characteristic emission peaks. The variation of IL intensity is studied in a YAlO3:Tb3+ crystal for a wide fluence range of 3.91 × 1012 –17.57 × 1012 ions cm−2. The IL intensity is found to be higher in lower ion fluences, and it decreases with the increase of ion fluence. Thermoluminescence (TL) studies are carried out for ion fluence– (3.91 × 1012 ions cm−2) and UV-exposed (05–60 min) single crystals. A single well-resolved glow peak at 242 °C, along with a shouldered peak at 272 °C, is recorded in the Tm3+-doped sample. In the Tb3+-doped samples, a well-resolved glow peak at 218 °C, along with a shouldered peak at 147 °C, is recorded at the lower temperature side. In the UV-exposed crystals, two glow peaks at 168 °C and 223 °C are recorded. The glow peaks are found to be shifted towards the lower temperature side with an increase in UV exposure time. Good linearity over a large span of UV exposure time and a single glow peak with a simple trap distribution are observed in YAlO3:Tb3+ single crystals, which makes them suitable as a dosimeter for UV-rays. The kinetic parameters (E, b, s) are estimated using the glow peak shape method for both ion and UV-exposed crystals, and the results are discussed in detail.

Source:IOPscience

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