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'perovskite' in keywords
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2000 (1)
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1Author    S. Frenzen, Hk Müller-BuschbaumRequires cookie*
 Title    Uber einen 9L-Perowskit der Zusammensetzung Ba9Ru3? 2Mn5?8027 On a 9L-Perovskite of the Composition Ba9Ru3 2Mn5 80 27  
 Abstract    Single crystals of Ba9Ru3 2Mn5 80 27 have been prepared by flux techniques. X-ray four circle diffractometer measurements led to trigonal (rhombohedral) symmetry, space group D3d-R 3 m , a = 5.7043(5), c = 21.255(4) A , Z = 1. This phase is isotypic to B a R u 0 3. The crystal structure and the occupation of the M3O i2 triple octahedra by ruthenium and manga­ nese are discussed with respect to other oxides containing M30 12 groups in an ordered and disordered way. 
  Reference    Z. Naturforsch. 50b, 585 (1995); eingegangen am 10. Oktober 1994 
  Published    1995 
  Keywords    Barium, Ruthenium, M anganese, Oxide, Perovskite, Structure 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-0585.pdf 
 Identifier    ZNB-1995-50b-0585 
 Volume    50 
2Author    I. Krabbes, H. LangbeinRequires cookie*
 Title    Herstellung von CuTa206 -von der Trirutil-zur Perowskit-Struktur Preparation o f CuTa20 6 -from the Trirutile to the Perovskite Structure  
 Abstract    A new trirutile MTa20 6 was synthesized by thermal decomposition of a freeze dried Cu-Ta-oxalate precursor. Its formation takes place preferentially starting from Cu-rich precursor compositions. Above 1000°C decomposition leads to the already known perovskite like structure with a composition Cuj .o.sTai 9S0 6 . The degree of the orthorhombic distortion of the perovskite unit cell depends on the conditions during the cooling process after perovskite formation. 
  Reference    Z. Naturforsch. 51b, 1605—1610 (1996); eingegangen am 18. März 1996 
  Published    1996 
  Keywords    Copper Tantalate, Thermal Decomposition, Perovskite, Trirutile, Metastable Compounds 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-1605.pdf 
 Identifier    ZNB-1996-51b-1605 
 Volume    51 
3Author    GaryL. Catchen, EdwardF. Hollinger, ToddM. RearickRequires cookie*
 Title    Characterizing Phase Transitions in the Perovskites PbTi0 3 and BaTi0 3 Using Perturbed-Angular-Correlation Spectroscopy  
 Abstract    Perturbed-angular-correlation (PAC) spectroscopy was used to measure in ceramic samples of PbTi0 3 and BaTi0 3 the temperature dependence of the Ti-site electric-field gradients (EFGs) at temperatures very close to the ferroelectric-to-paraelectric transition temperatures T c . The samples were doped with small amounts of Hf that carried the 181 Hf — l8l Ta probe radioactivity. A high-frequency nuclear quadrupole interaction that decreases very little as the temperature approaches T c , characterizes the PbTi0 3 transition. The tetragonal and cubic phases for PbTi0 3 appear to coexist over a temperature interval of 8 ± 1 K, and the transition shows a thermal hysteresis of about 4 K. In contrast, a lower-frequency interaction that decreases rapidly as temperature approaches T c , characterizes the BaTiO, transition. Both phases of BaTi0 3 appear to coexist over an interval of about 2 K, and the thermal hysteresis is about 1 K. At temperatures above T c , both PbTi0 3 and BaTi0 3 show weak, non-vanishing Ti-site EFGs. Although, for BaTi0 3 , this effect limits the accuracy with which critical effects can be measured, we estimate a power-law exponent ß = 0.21 ± 0.05, which most likely is somewhat lower in magnitude than the actual critical exponent. For the explanation of our observations we assume the existence of a distribution of T c -values. This distribution would arise because the crystals could have spatially non-uniform distributions of nucleation sites, which for PbTi0 3 and BaTi0 3 could be point defects. 
  Reference    Z. Naturforsch. 51a, 411—421 (1996); received November 20 1995 
  Published    1996 
  Keywords    Ferroelectric, perovskite, nuclear electric-quadrupole, perturbed-angular-correlations, phase transition 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0411.pdf 
 Identifier    ZNA-1996-51a-0411 
 Volume    51 
4Author    P. De, La Presa, K. P. Lieb, M. Uhrmacher, L. ZiegelerRequires cookie*
 Title    Perturbed Angular Correlation Studies in SrTi0 3 Single Crystals  
 Abstract    The quadrupole hyperfine interactions of 11 'Cd/ 111 In probe nuclei in single-crystalline SrTi0 3 perovskite samples were investigated using Perturbed Angular Correlation spectroscopy. Three electric field gradients were detected and their fractions and hyperfine parameters were measured in the temperature range from 26 to 700 K. The fraction / 0 having a vanishing quadrupole frequency, as expected for 111 Cd on substitutional sites in a cubic lattice, starts to develop around 300 K and reaches 100% at 700 K. Two well-defined EFG's having closely lying quadrupole frequencies and asymmetry parameters of cj qi = 49.1(3) Mrad/s, 77, = 0.10(2) and u Q2 = 51.8(3) Mrad/s, r] 2 = 0.12(2), at room temperature, were identified in the temperature range from 250 to 530 K, and their (100) orientation in the lattice was determined. They are associated with electronic defects at the probe atoms. 
  Reference    Z. Naturforsch. 55a, 237—241 (2000); received August 24 1999 
  Published    2000 
  Keywords    Perturbed Angular Correlations, SrTi0 3, Single Crystal, Electronic Defects, Perovskite 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0237.pdf 
 Identifier    ZNA-2000-55a-0237 
 Volume    55