Search

Abstract: We report the hydrothermal synthesis of AlPO4-5 crystals using TBAOH as template. The resulting product sensitively depends on the gel compositions and synthesis procedure. By treating the tri-isopropylate aluminum gel solution with ultrasonic, and adding HF acid to adjust the gel pH value, perfect hexagonal-shaped AlPO4-5 crystals are obtained. At high TBAOH content, some centrosymmetric intersecting crystals are observed in the products, this can be interpreted by the polar growth of AlPO4-5 crystals. The decomposition of template TBAOH in the channels of AlPO4-5 crystals has been studied by FTIR and TG analysis. [Copyright &y& Elsevier]

Abstract: Na0.5Bi0.5TiO3 thin films have been grown on p-type Si(111) and Pt/Ti/SiO2/Si substrates by a method of chemical solution decomposition. The structure and microscopy were studied by X-ray diffraction and atomic force microscopy, respectively. The electrical measurements were conducted on metal–ferroelectric–semiconductor or metal–ferroelectric–metal capacitors. The films show low leakage current. They also exhibit good ferroelectric and dielectric properties. [Copyright &y& Elsevier]

Abstract: We report the effects of gel composition and crystallization condition on the hydrothermal synthesis of optical-clear large AlPO4-5 crystals. By using a gel with excessive Al species and high HF content, large perfect hexagonal-shaped AlPO4-5 crystals (size 1.25mm×0.65mm) were obtained, at a synthesis temperature of 453K with a crystallization period of 36h. The optical quality of the crystals is sensitive to the crystallization temperature and time duration. [Copyright &y& Elsevier]

Samarium-doped Bi4Ti3O12 (Bi3.15Sm0.85Ti3O12) thin films have been prepared on SiO2/p-Si(1 1 1) substrate by spin coating metalorganic solution decomposition method. The structural properties of the films were examined by X-ray diffraction. The surface morphology and quality were studied using atomic force microscopy. The films exhibit excellent insulating properties and resistance to breakdown. The clockwise hysteresis curve shows that the films are polarization-type switching and the memory window is about 1.2 V. The dielectric constant and dissipation factor at a frequency of 100 kHz are 100 and 0.15, respectively. [Copyright &y& Elsevier]

Abstract: Bi3.15Pr0.85Ti3O12 thin films have been grown on a p-type Si(111) substrate by the method of metalorganic sol decomposition and spin coating. The optimum temperature of crystallization is 680°C. Atomic force microscopy reveals that the films have a dense, smooth surface. The electrical measurements were conducted on a metal–ferroelectric–insulator–semiconductor capacitor. The films exhibit good insulating property at room temperature. The clockwise hysteresis curves observed show that the films have a memory effect. The fixed charge density and the surface state density were also calculated. The results show that the films have promising applications as the ferroelectric field effect transistor memories. [Copyright &y& Elsevier]

The metal–ferroelectric–insulator–semiconductor (MFIS) structure has been fabricated using Bi3.54Nd0.46Ti3O12 (BNdT) as a ferroelectric layer. The BNdT films can crystallize well at 700°C for 1 h. The J–V curve shows the MFIS structure has a good insulating property. C–V hysteresis loops at various sweeping speed were collected as were polarization types. The leakage current density, dielectric constant and dielectric loss were found to be dependent on the annealing temperature. The dielectric constant and dielectric loss at a frequency of 100 kHz are 98 and 0.092, respectively. [Copyright &y& Elsevier]

Neodymium-doped Bi4Ti3O12 (Bi3.15Nd0.85Ti3O12) films have been synthesized by metalorganic solution decomposition method and deposited on SiO2/p-Si(1 1 1) substrate by spin coating. The structural characteristic and crystallization of the films were examined by X-ray diffraction. The surface morphology and quality were studied using atomic force microscope. The films exhibit good insulating property and resistance to breakdown. The clockwise hysteresis curve is referred to as polarization type switching, and the memory window is about 2.5 V. The dielectric constant and dissipation factor at a frequency of 100 kHz are 110 and 0.137, respectively, at room temperature. [Copyright &y& Elsevier]

Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290–2000 nm have been recorded at room temperature. The Judd–Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels. [Copyright &y& Elsevier]