Single crystal growth of the tetragonal tungsten bronze CaxBa1−xNb2O6 (x=0.28; CBN-28) (original) (raw)
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Journal of Applied …, 2008
Dielectric properties, microstructures, and phase transition behaviors of ␣ and  phases of CaxBa 1−x Nb 2 O 6 ͑x = 0.22, 0.30, and 0.38͒ ceramics were investigated. All the three compositions had partially filled tungsten-bronze structure ͑TTB͒ and relatively high Curie temperatures ͑up to 345°C͒ compared with Sr 1−x Ba x Nb 2 O 6 . The ␣ phase exhibits unambiguously a diffused phase transition, while the  phase is associated with an incommensurate phase and needs to be further studied. The dielectric and ferroelectric properties of Ca x Ba 1−x Nb 2 O 6 ceramics were strongly processing-dependent. A mechanism was proposed to explain the grain growth behavior of TTB ceramic niobates.
Journal of Applied Physics, 2008
Dielectric properties, microstructures, and phase transition behaviors of ␣ and  phases of CaxBa 1−x Nb 2 O 6 ͑x = 0.22, 0.30, and 0.38͒ ceramics were investigated. All the three compositions had partially filled tungsten-bronze structure ͑TTB͒ and relatively high Curie temperatures ͑up to 345°C͒ compared with Sr 1−x Ba x Nb 2 O 6 . The ␣ phase exhibits unambiguously a diffused phase transition, while the  phase is associated with an incommensurate phase and needs to be further studied. The dielectric and ferroelectric properties of Ca x Ba 1−x Nb 2 O 6 ceramics were strongly processing-dependent. A mechanism was proposed to explain the grain growth behavior of TTB ceramic niobates.
Crystal Research and Technology, 2003
Calcium barium niobate (CBN), also like strontium barium niobate (SBN), belongs to the materials family of partially filled tetragonal tungsten bronzes, which show relaxor-type ferroelectric phase transitions and large electro-optic effects. For the first time, it was possible to grow large single crystals of Ca 0.25 Ba 0.75 Nb 2 O 6 (CBN-25) and CBN-28 by using different growing techniques. The successful single crystal growth allowed to investigate several physical properties of the novel phase. Herein, we report on measurements of differential thermal analysis (DTA), wavelength dispersion of the refractive indices, temperature dependence of the birefringence and light absorption. Additionally, results of the single crystal X-ray structure analysis are presented.
Materials Research Bulletin, 2009
Single crystals of (1 − x)BaTiO3 + xNaNbO3 (BTNN) for x = 0.84 were obtained by high temperature solution growth using Na2B4O7 as solvent. The room temperature crystal structure of BTNN 16/84-phase was determined from X-ray single crystal diffraction data, in the tetragonal system with space group P4bm. The refinement from 246 independent reflections led to the following parameters: a = b = 5.5845(3) Å, c = 3.9453(2) Å, V = 123.041(11) Å3, Z = 2, with final cRwp = 0.150 and RB = 0.041. The structure of BTNN 16/84-phase can be described as a three-dimensional framework built up from (Nb–Ti)O6 octahedra with Na and Ba in the dodecahedral site of perovskite-like type. Some mm3-sized crystals have been selected and various dielectric measurements (ferroelectric, pyroelectric, and piezoelectric) have been performed. Transition from paraelectric to ferroelectric state at around 460 K has been observed to be in good agreement with ceramics of closer composition. Dielectric, piezoelectric and pyroelectric measurements on crystal confirm the ferroelectric behaviour of BTNN 16/84.
Eurasian Chemico-Technological Journal
The International Higher Education Academy of Sciences Eurasian Chemico-Technological Journal Quarterly Journal of the International Higher Education Academy of Sciences The Eurasian Chemico-Technological Journal is an international, peer-reviewed journal covering all branches of chemistry and chemical technology. The Journal particularly welcomes papers on new materials and chemical technologies, modern problems of organic synthesis, physical chemistry and chemical physics, solid state and soft matter research, electro-, photo-, radiation-and plasma-chemistry, colloids and nanotechnology, catalysis and surface science, polymers. The Journal publishes reviews and full research articles. We also welcome contributions based on the research presented at the conferences held in Europe and Asia. All submitted manuscripts are peer-reviewed by the members of the Editorial Board and international referees.
Strontium–barium niobate single crystals, growth and ferroelectric properties
Journal of Crystal Growth, 2008
Single crystals of strontium-barium niobate Sr x Ba 1Àx Nb 2 O 6 (SBN) undoped and doped with Ce or Cr were grown by the Czochralski method. The inductive heating system was used. In order to improve conditions of growth, a crucible-base cooling was introduced. Single crystals of the following nominal compositions have been obtained: Sr 0.4 Ba 0.6 Nb 2 O 6 , Sr 0.5 Ba 0.5 Nb 2 O 6 , Sr 0.61 Ba 0.39 Nb 2 O 6 (congruent melting) and Sr 0.75 Ba 0.25 Nb 2 O 6 , designated hereafter as SBN40, SBN50, SBN61 and SBN75. They were up to 22 mm in diameter and 40 mm in length with characteristic 24 faces, free from striations and other extended defects. All the crystals were grown in the [0 0 1] direction. The dopants (Ce or Cr) were added to the SBN61 composition. By use of ICP-OES method, the chemical compositions were checked. Etch pit density was also measured. In the case of the undoped single crystals, it was found to be 2.4 Â 10 2-5.6 Â 10 3 cm À2 but in the case of Ce or Cr doping, it increased up to 3.6 Â 10 4-1.8 Â 10 5 cm À2. Investigations of the linear dielectric response measured within 10 0 pfp10 5 Hz along the polar c-axis of four obtained singlecrystalline SBN compounds revealed a gradual crossover from conventional ferroelectric (SBN40) to extreme relaxor (SBN75) behavior.
International journal of innovation and scientific research, 2016
In this work, lead barium niobate tetragonal tungsten bronze structured ceramics modified with Gd 3+ with the stochiometric formula Pb x-3y/2Gd yBa 1-xNb 2O6, where y=0 - 10 mol% Gd 3+ , were fabricate through the solid state reaction method and investigated for structural and Raman properties. The dried powders were calcined at 800°C for 6h and one sample was calcined at 1050°C for 20h. As it can be observed, there is a mixture of tetragonal and orthorhombic phases. The analysis of the Raman spectra allowed a clear identification of the phase evolution Kinetics as a function of the calcining temperature.