Thermal and X-Ray Diffraction Studies of Doped and Undoped Single Crystal and Polycrystalline BaTiO3

1994 ◽  
Vol 360 ◽  
Author(s):  
L.G. Carreiro ◽  
J.V. Marzik ◽  
K.K Deb
Keyword(s):  
Solid Solution ◽  
Curie Temperature ◽  
Single Crystal ◽  
Dopant Concentration ◽  
Infrared Detection ◽  
Thermal Transition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Mole Percent ◽  
X Ray

AbstractCalorimetric changes in a series of pure and doped single crystal and polycrystalline BaTiO3 were studied using differential scanning calorimetry over the temperature range of-110°C to 200°BC. The dopants, oxides of niobium and iron were varied from 0.5 to 8 mole percent, and strontium was varied from 5 to 35 mole percent. Endotherms were observed corresponding to three crystallographic transitions. The highest observed thermal transition corresponds to a tetragonal to cubic crystallographic transition and is also associated with the Curie temperature in these materals. Two additional endothermic transitions were also observed, an intermediatetemperature orthorhombic to tetragonal transition, and a low-temperature rhombohedral to orthorhombic transition. The three dopants decreased the crystallographic transition temperatures and Curie temperature as the dopant concentration was increased. X-ray diffraction was used to identify phases present and to determine the extent of solid solution. It is expected that these materials will display improved infrared detection as well as opto-electronic properties.

Crystal chemistry of lamprophyllite-group minerals from the Murun alkaline complex (Russia) and pegmatites of Rocky Boy and Gordon Butte (USA): single crystal X-ray diffraction and Raman spectroscopy study

2021 ◽  
Vol 77 (2) ◽  
Author(s):  
Sergey M. Aksenov ◽  
Anastasia D. Ryanskaya ◽  
Yuliya V. Shchapova ◽  
Nikita V. Chukanov ◽  
Nikolay V. Vladykin ◽  
...  
Keyword(s):  
Solid Solution ◽  
Single Crystal ◽  
Raman Spectra ◽  
Crystal Chemistry ◽  
Solid Solution Series ◽  
X Ray Diffraction ◽  
Alkaline Complex ◽  
Oh Groups ◽  
X Ray ◽  
Solution Series

Specific features of the crystal chemistry of lamprophyllite-group minerals (LGMs) are discussed using the available literature data and the results of the single-crystal X-ray diffraction and a Raman spectroscopic studies of several samples taken from the Murun alkaline complex (Russia), and Rocky Boy and Gordon Butte pegmatites (USA) presented here. The studied samples are unique in their chemical features and the distribution of cations over structural sites. In particular, the sample from the Gordon Butte pegmatite is a member of the barytolamprophyllite–emmerichite solid solution series, whereas the samples from the Murun alkaline complex and from the Rocky Boy pegmatite are intermediate members of the solid solution series formed by lamprophyllite and a hypothetical Sr analogue of emmerichite. The predominance of O2− over OH− and F− at the X site is a specific feature of sample Cha-192 from the Murun alkaline complex. New data on the Raman spectra of LGMs obtained in this work show that the wavenumbers of the O—H stretching vibrations depend on the occupancies of the M2 and M3 sites coordinating with (OH)− groups. Cations other than Na+ and Ti4+ (mainly, Mg and Fe3+) can play a significant role in the coordination of the X site occupied by (OH)−. Data on polarized Raman spectra of an oriented sample indicate that the OH groups having different local coordinations have similar orientations with respect to the crystal. The calculated measures of similarity (Δ) for lamprophyllite and ericssonite are identical (0.157 and 0.077 for the 2M- and 2O-polytypes, respectively), which indicates that these minerals are crystal-chemically isotypic and probably should be considered within the same mineral group by analogy to the other mineralogical groups which combine isotypic minerals.

The structures and phase transitions in 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2]

2019 ◽  
Vol 75 (6) ◽  
pp. 1144-1151
Author(s):  
Tamara J. Bednarchuk ◽  
Wolfgang Hornfeck ◽  
Vasyl Kinzhybalo ◽  
Zhengyang Zhou ◽  
Michal Dušek ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Single Crystal ◽  
Room Temperature ◽  
Variable Temperature ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Hybrid Compound ◽  
Space Group ◽  
X Ray

The organic–inorganic hybrid compound 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2] (4apFeS), was obtained by slow evaporation of the solvent at room temperature and characterized by single-crystal X-ray diffraction in the temperature range from 290 to 80 K. Differential scanning calorimetry revealed that the title compound undergoes a sequence of three reversible phase transitions, which has been verified by variable-temperature X-ray diffraction analysis during cooling–heating cycles over the temperature ranges 290–100–290 K. In the room-temperature phase (I), space group C2/c, oxygen atoms from the closest Fe-atom environment (octahedral) were disordered over two equivalent positions around a twofold axis. Two intermediate phases (II), (III) were solved and refined as incommensurately modulated structures, employing the superspace formalism applied to single-crystal X-ray diffraction data. Both structures can be described in the (3+1)-dimensional monoclinic X2/c(α,0,γ)0s superspace group (where X is ½, ½, 0, ½) with modulation wavevectors q = (0.2943, 0, 0.5640) and q = (0.3366, 0, 0.5544) for phases (II) and (III), respectively. The completely ordered low-temperature phase (IV) was refined with the twinning model in the triclinic P{\overline 1} space group, revealing the existence of two domains. The dynamics of the disordered anionic substructure in the 4apFeS crystal seems to play an essential role in the phase transition mechanisms. The discrete organic moieties were found to be fully ordered even at room temperature.

New crystal structures in the realm of 5,5′-azotetrazolates

2015 ◽  
Vol 70 (2) ◽  
pp. 125-134 ◽  
Author(s):  
Martin Lampl ◽  
Gerhard Laus ◽  
Doris E. Braun ◽  
Volker Kahlenberg ◽  
Klaus Wurst ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Single Crystal ◽  
Crystal Structures ◽  
Organic Cations ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Diffraction Patterns

AbstractThe preparation of six new 5,5′-azotetrazolates with organic cations is reported. Differential scanning calorimetry of all compounds showed exothermic decompositions. The crystal structures of the six 5,5′-azotetrazolates were determined by single-crystal X-ray diffraction analyses. The phase purities of the bulk samples were confirmed by Pawley fits of the experimental and calculated powder X-ray diffraction patterns.

Structure and properties of Al–Mg mechanical alloys

2003 ◽  
Vol 18 (8) ◽  
pp. 1827-1836 ◽  
Author(s):  
Mirko Schoenitz ◽  
Edward L. Dreizin
Keyword(s):  
Solid Solution ◽  
Energetic Materials ◽  
Amorphous Material ◽  
Bulk Composition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Diffraction Microscopy

Mechanically alloys in the Al–Mg binary system in the range of 5–50 at.% Mg were produced for prospective use as metallic additives for propellants and explosives. Structure and composition of the alloys were characterized by x-ray diffraction microscopy (XRD) and scanning electron microscopy. The mechanical alloys consisted of a supersaturated solid solution of Mg in the α aluminum phase, γ phase (Al12Mg17), and additional amorphous material. The strongest supersaturation of Mg in the α phase (20.8%) was observed for bulk Mg concentrations up to 40%. At 30% Mg, the γ phase formed in quantities detectable by XRD; it became the dominating phase for higher Mg concentrations. No β phase (Al3Mg2) was detected in the mechanical alloys. The observed Al solid solution generally had a lower Mg concentration than the bulk composition. Thermal stability and structural transitions were investigated by differential scanning calorimetry. Several exothermic transitions, attributed to the crystallization of β and γ phases were observed. The present work provides the experimental basis for the development of detailed combustion and ignition models for these novel energetic materials.

Glass-Coated Cu-Mn-Ga Microwires Produced by Taylor-Ulitovsky Technique

2009 ◽  
Vol 152-153 ◽  
pp. 79-84 ◽  
Author(s):  
Joan Josep Suñol ◽  
L. Escoda ◽  
C. García ◽  
V.M. Prida ◽  
Victor Vega ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solid Solution ◽  
Curie Temperature ◽  
Energy Dispersive Spectroscopy ◽  
Room Temperature ◽  
Alloy Composition ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Magnetic Field

Glass-coated Cu-Mn-Ga microwires were fabricated by Taylor-Ulitovsky technique. By means of energy dispersive spectroscopy microanalysis, an average alloy composition of Cu56Ga28Mn16 was determined. The temperature dependence of magnetization measured at a low magnetic field showed the coexistence of two ferromagnetic phases. The Curie temperature of one phase is 125 K and above room temperature for the other one. X-ray diffraction at room temperature and at 100 K reflects the presence of the same three crystalline phases corresponding to the cubic B2 Cu-Mn-Ga structure as a main phase and the minor phases of fcc Cu rich solid solution with Mn and Ga and the monoclinic CuO.

Low-temperature phase transition in glycine–glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry

2012 ◽  
Vol 68 (3) ◽  
pp. 287-296 ◽  
Author(s):  
Boris A. Zakharov ◽  
Evgeniy A. Losev ◽  
Boris A. Kolesov ◽  
Valeri A. Drebushchak ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Raman Spectroscopy ◽  
Single Crystal ◽  
Glutaric Acid ◽  
Group Symmetry ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

The occurrence of a first-order reversible phase transition in glycine–glutaric acid co-crystals at 220–230 K has been confirmed by three different techniques – single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P21/c to P\bar 1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

The synthesis of NbSi2 by mechanical alloying

1997 ◽  
Vol 12 (5) ◽  
pp. 1172-1175 ◽  
Author(s):  
Taiping Lou ◽  
Guojiang Fan ◽  
Bingzhe Ding ◽  
Zhuangqi Hu
Keyword(s):  
Solid Solution ◽  
Differential Scanning Calorimetry ◽  
Intermetallic Compound ◽  
Mechanical Alloying ◽  
Ball Milling ◽  
Temperature Rise ◽  
Milling Time ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

The stoichiometric intermetallic compound NbSi2 has been synthesized by mechanical alloying (MA) elemental Nb and Si powders. The alloying process has been investigated by means of x-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was found that the formation of the Nb2Si intermetallic compound occurs abruptly after 65 min of milling without any interruptions during the alloying process. However, short interruptions at a 5 min interval during ball milling result in a gradual reaction for the formation of the NbSi2 compound as well as a new metastable bcc structured solid solution. We conclude that the temperature rise during mechanical alloying plays an important role in initiating the abrupt reaction after an incubation milling time.

Growth and luminescence properties of Pr3+-doped LaCl3 single crystal

2016 ◽  
Vol 09 (02) ◽  
pp. 1650022
Author(s):  
Zihan Liu ◽  
Qinhua Wei ◽  
Laishun Qin ◽  
Hongsheng Shi ◽  
Kangying Shu
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Ultra Violet ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Xrd Pattern ◽  
X Ray ◽  
Decay Times ◽  
Vertical Bridgman ◽  
Dominant Peak

A transparent LaCl3:Pr[Formula: see text] single crystal with a dimension of [Formula: see text] [Formula: see text][Formula: see text]mm was grown by vertical Bridgman method. The differential scanning calorimetry (DSC) shows that the melting point of LaCl3:Pr[Formula: see text] crystal is about 841.5[Formula: see text]C. The powder X-ray diffraction (XRD) pattern proves the crystal structure of LaCl3:Pr[Formula: see text] is hexagonal with space group P63/m. There is a dominant peak centered at 335[Formula: see text]nm and a weaker peak located at 400[Formula: see text]nm under X-ray excitation, while three peaks located at 335[Formula: see text]nm, 356[Formula: see text]nm and 400[Formula: see text]nm under ultra-violet. The peaks of 335[Formula: see text]nm and 356[Formula: see text]nm can be ascribed to the transition of 5d–4f of Pr[Formula: see text], while the 400[Formula: see text]nm maybe related to LaCl3 host. Decay times were fitted to be about 14.5[Formula: see text]ns for 335[Formula: see text]nm, 14.6[Formula: see text]ns for 356[Formula: see text]nm and 1.3[Formula: see text]ns for 400[Formula: see text]nm. The experimental results show that the LaCl3:Pr[Formula: see text] crystal will be a promising scintillator.

The solid solution between platinum and palladium in nature

2013 ◽  
Vol 77 (3) ◽  
pp. 269-274 ◽  
Author(s):  
L. Bindi ◽  
F. Zaccarini ◽  
G. Garuti ◽  
N. Angeli
Keyword(s):  
Solid Solution ◽  
Single Crystal ◽  
Structural Data ◽  
Micro Hardness ◽  
Metallic Elements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Complete Solid Solution ◽  
Hardness Values ◽  
Palladium Platinum

AbstractChemical and structural data are reported for platinum–palladium intermediates from two nuggets found at Córrego Bom Sucesso, Minas Gerais, Brazil. Three grains with simple stoichiometries (i.e. PtxPd1−x with x ∼0.67, ∼0.5 and ∼0.33, which correspond to Pt2Pd, PtPd and PtPd2, respectively) were characterized by single-crystal X-ray diffraction and electron-probe microanalysis. In the absence of single-crystal data it might be tempting to hypothesize that such simple stoichiometries represent distinct mineral species, however structural analyses show that all of the phases are cubic and crystallize in space group Fmm. They are, therefore, natural intermediates in the palladium–platinum solid solution. Reflectance and micro-hardness values are reported for the samples and a comparison with the pure metallic elements made. On the basis of information gained from the chemical and structural characterization it can be concluded that there is a complete solid solution between Pt and Pd in nature. These findings corroborate results from experiments on synthetic compounds.

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