The β &lt;-&gt; α' phase transition of Sr2SiO4. I. Order–disorder in the structure of the α' form at 383 K

Catti, M.; Gazzoni, G.; Ivaldi, Gabriella; Zanini, G.

doi:10.1107/s0108768183003213

Cited by 88 publications

(68 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The temperature read by the working thermometer was checked by a thermocouple located at the sample position. The crystals of Sr2SiO4 previously synthetized (Catti, Gazzoni & Ivaldi, 1983) showed {001 }, { 101 } and {011 } as dominant forms. Polysynthetic twinning with (100) contact plane and very thin lamellar domains was present in all crystals observed along the [010] direction; those with smallest [010] elongation and largest {011} development were selected, together with a few showing {010} tabular habit, so as to attain the best conditions of observation of twin domains in the fl phase.…”

Section: Optical Microscopymentioning

confidence: 99%

“…Clearly F is a pseudosymmetry operation of the crystal structure itself. Using the orthogonal absolute atomic coordinates X t = a(x I -¼) sin fl, Yl = bYl, Zt = czt + a(x i --~) cos fl, the F operation simply transforms X t into -X~, and the atomic displacements, A, can be calculated on the basis of the ~Sr2SiO4 structural data (Catti, Gazzoni & Ivaldi, 1983). The results are reported in Table 3.…”

Section: Ferroelastielty Ofp-sr2siomentioning

confidence: 99%

“…In the frame of an investigation of the crystal chemistry and the polymorphism of alkaline-earth orthosilicates, the structures of fl-Sr2SiO 4, monoclinic P2~/n (Catti, Gazzoni & Ivaldi, 1983), and of tx'-Sr2SiO 4, orthorhombic Pmnb (Catti, Gazzoni, Ivaldi & Zanini, 1983), were previously determined from the same crystal at 298 and 383 K, respectively. The transition between the low-fl and the high-a' forms is reported by Pieper, Eysel & Hahn (1972) to occur at about 358 K by DTA measurements, with a small but significant enthalpy change of 210 J mol -~ (DSC results).…”

Section: Introductionmentioning

confidence: 99%

“…The thermal properties of the phase change and the fl---a' lattice relationships should be related to the positional order-disorder observed in high-temperature Sr2SiO 4. Moreover, since the lowtemperature fl phase shows twin domains (Catti, Gazzoni & Ivaldi, 1983) and can be formally classified as Aizu's (1969) ferroelastic species mmmF2/m, the possible presence of true ferroelastic behaviour is also investigated in this work.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The β <-> α' phase transition of Sr₂SiO₄. II. X-ray and optical study, and ferroelasticity of the β form

Catti¹,

Gazzoni²

1983

Acta Crystallogr B Struct Sci

Self Cite

View full text Add to dashboard Cite

The transition between the monoclinic fl and orthorhombic a' phases of strontium orthosilicate was investigated by single-crystal diffractometry and polarizing microscopy at variable temperatures, on the basis of the disappearance or appearance of twin domains of the fl form. The phase change occurred sharply with thermal hysteresis in both experiments, at 364 and 355 K (X-rays) and at 369 and 359 K (light, best values out of a number of samples) for fl --, a' and a' --, fl, respectively; the optical study showed that transition temperatures are influenced by the size and habit of crystals. The orientations of fl and a' lattices are related by a simple rotation of the x axis. A first-order character is suggested by thermal results for the phase change, though it relates ordered and disordered structures. Crystals of fl-Sr2SiO 4 prove to be ferroelastic (Aizu's species mmmF2/m) with a spontaneous strain of 0.033. The mechanisms of the phase transition and of the transformation between mirrorrelated orientation states are discussed in relation to structural disorder of the paraelastic a' form.

show abstract

Section: Optical Microscopymentioning

confidence: 99%

Section: Ferroelastielty Ofp-sr2siomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The β <-> α' phase transition of Sr₂SiO₄. II. X-ray and optical study, and ferroelasticity of the β form

Catti¹,

Gazzoni²

1983

Acta Crystallogr B Struct Sci

Self Cite

View full text Add to dashboard Cite

show abstract

“…A reação fica mais lenta porque o produto formado na interface impede o contato entre os reagentes em razão da baixa energia térmica. como sendo B para a temperatura e aplica-se a distributiva de p no expoente da equação (16). Ao produto px atribui-se a variável at para tempo e bT para temperatura.…”

Section: Estruturaunclassified

Ortossilicatos: uma nova proposta para a cinética de formação de Sr2SiO4 em estado sólido de uma comparação de rotas de síntese de Zn2SiO4 dopado com Mn2+

Soares¹

View full text Add to dashboard Cite

Photoluminescent Materials for Solid‐State Lighting: State of the Art and Future Challenges

Meyer

Tappe

2015

Advanced Optical Materials

198

110

View full text Add to dashboard Cite

• Control over purity and particle morphology.• Non-hazardous.• Reasonable production costs.While for certain conversion colors solutions close to the ideal have been found, there remains work to be done, especially for phosphors which emit in the red. This article will highlight the classic solutions for white pcLEDs and show the remaining challenges. In addition, an account will be given of recent developments involving semiconductor light sources with high radiance and high lumen output, where the color conversion of blue laser diodes for digital projection and automotive applications poses new challenges to materials research. Luminescent Materials: The State of the Art Yellow-Emitting MaterialsToday, almost all single-phosphor pcLEDs are based on Ce 3+ -doped yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG:Ce) [ 5,6 ] or, sometimes, Eu 2+ -doped orthosilicate phosphors (Sr, Ba, Mg) 2 SiO 4 , [7][8][9][10][11][12][13] as the yellow-emitting luminescent material. However, stability issues of the orthosilicates have not been fully overcome: this has limited the commercial use of this material class.The emission color of YAG:Ce can be tuned by substitution of lattice constituents, e.g., Y may be replaced by Lu (Lutetium), Gd (Gadolinium), or Tb (Terbium), and Al may be replaced by Ga (Gallium). The emission spectrum is shown in Figure 1 . This material fulfi lls all of the stated requirements and therefore can be considered an archetypal LED phosphor material. [ 14,15 ] The excitation spectrum for YAG:Ce at 440-460 nm is well matched to the emission of blue LEDs and its yellow dual ground-state broadband emission in the visible spectral region (500-700 nm) provides a reasonable CRI. Such a single-phosphor approach may be very simple and effi cient, but it has one major drawback: the limited spectral power distribution in the red spectral range causes a CCT > 4000 K (cool white light) and a low CRI (usually below 80). Particularly for indoor illumination, a higher CRI and lower (i.e., warmer) CCT (2700-3200 K) are preferable. Suitable white light LEDs can be produced using a two-phosphor approach, wherein a yellow phosphor (YAG:Ce) is combined with a red one.The effi cient generation of white light by phosphor-converted LEDs (pcLEDs) suffers from a trade-off between high color rendition, low correlated color temperatures, and luminous effi cacy. While this is partially an inherent problem, it is also caused by the spectral effi ciency of the materials used. The particular challenges for materials research lie, amongst the demanding general requirements, in fi nding very narrow-band or line-emitting materials: excitable with blue light, emitting in the near red. A way to design Mn(IV) activated line emitters is proposed, and methods for high-throughput combinatorial syntheses are specifi ed.

show abstract

The β <-> α' phase transition of Sr₂SiO₄. I. Order–disorder in the structure of the α' form at 383 K

Cited by 88 publications

References 2 publications

The β <-> α' phase transition of Sr₂SiO₄. II. X-ray and optical study, and ferroelasticity of the β form

The β <-> α' phase transition of Sr₂SiO₄. II. X-ray and optical study, and ferroelasticity of the β form

Ortossilicatos: uma nova proposta para a cinética de formação de Sr<sub>2</sub>SiO<sub>4</sub> em estado sólido de uma comparação de rotas de síntese de Zn<sub>2</sub>SiO<sub>4</sub> dopado com Mn<sup>2+</sup>

Photoluminescent Materials for Solid‐State Lighting: State of the Art and Future Challenges

Contact Info

Product

Resources

About

The β <-> α' phase transition of Sr2SiO4. I. Order–disorder in the structure of the α' form at 383 K

Cited by 88 publications

References 2 publications

The β <-> α' phase transition of Sr2SiO4. II. X-ray and optical study, and ferroelasticity of the β form

The β <-> α' phase transition of Sr2SiO4. II. X-ray and optical study, and ferroelasticity of the β form

Ortossilicatos: uma nova proposta para a cinética de formação de Sr<sub>2</sub>SiO<sub>4</sub> em estado sólido de uma comparação de rotas de síntese de Zn<sub>2</sub>SiO<sub>4</sub> dopado com Mn<sup>2+</sup>

Photoluminescent Materials for Solid‐State Lighting: State of the Art and Future Challenges

Contact Info

Product

Resources

About

The β <-> α' phase transition of Sr₂SiO₄. I. Order–disorder in the structure of the α' form at 383 K

The β <-> α' phase transition of Sr₂SiO₄. II. X-ray and optical study, and ferroelasticity of the β form

The β <-> α' phase transition of Sr₂SiO₄. II. X-ray and optical study, and ferroelasticity of the β form