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Title: CeAlO{sub 3} and Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd) solid solutions: Crystal structure, thermal expansion and phase transitions

Abstract

The crystal structures of CeAlO{sub 3} and the solid solutions Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd), and their thermal behaviour in a wide temperature range of 12-1200 K have been precisely determined by means of in situ high-resolution X-ray powder diffraction technique applying synchrotron radiation, thermal analysis and magnetic measurements. The unique sequence of the reversible phase transitions I4/mcm{r_reversible}Imma{r_reversible}R3-barc{r_reversible}Pm3-barm has been detected in CeAlO{sub 3} and solid solutions formed in the pseudo-binary system CeAlO{sub 3}-LaAlO{sub 3}. In the Ce{sub 1-} {sub x} Nd {sub x} AlO{sub 3} system, the samples with x=0.3 and 0.5 compositions undergo three phase transformations I2/m{r_reversible}Imma{r_reversible}R3-barc{r_reversible}Pm3-barm, whereas for the Ce-rich sample Ce{sub 0.9}Nd{sub 0.1}AlO{sub 3} four successive transitions are observed: I4/mcm{r_reversible}I2/m{r_reversible}Imma{r_reversible}R3-barc{r_reversible}Pm3-barm. = Crystal structure parameters of all structural polymorphs of CeAlO{sub 3} and solid solutions based on them as well as their thermal evolution are reported. Based on in situ powder diffraction and DTA/DSC data, the phase diagrams of the pseudo-binary systems CeAlO{sub 3}-LaAlO{sub 3} and CeAlO{sub 3}-NdAlO{sub 3} are constructed together with a combined phase diagram, where the transition temperatures are presented as a function of the average radius of rare-earth cations. - Graphical abstract: Combined phase diagram of the CeAlO{sub 3}-LaAlO{submore » 3} and CeAlO{sub 3}-NdAlO{sub 3} systems, where the transition temperatures are presented as a function of the average radius of rare-earth cations. The letters indicate L iquid, C ubic, R hombohedral, O rthorhombic, M onoclinic and T etragonal phase fields.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [3];  [5];  [4];  [6]
  1. Institute of Telecommunications, Radioelectronics and Electronics Technique, Semiconductor Electronics Department, Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv (Ukraine), E-mail: crystal-lov@polynet.lviv.ua
  2. Institute of Telecommunications, Radioelectronics and Electronics Technique, Semiconductor Electronics Department, Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv (Ukraine)
  3. (Germany)
  4. Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt (Germany)
  5. Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, 01187 Dresden (Germany)
  6. (Spain)
Publication Date:
OSTI Identifier:
21015775
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 4; Other Information: DOI: 10.1016/j.jssc.2007.01.020; PII: S0022-4596(07)00039-4; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINATES; CALORIMETRY; CERIUM COMPOUNDS; CRYSTAL-PHASE TRANSFORMATIONS; DIFFERENTIAL THERMAL ANALYSIS; LANTHANUM COMPOUNDS; NEODYMIUM COMPOUNDS; PHASE DIAGRAMS; SOLID SOLUTIONS; SYNCHROTRON RADIATION; TEMPERATURE RANGE 0000-0013 K; TEMPERATURE RANGE 0013-0065 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K; THERMAL EXPANSION; TRANSITION TEMPERATURE; X-RAY DIFFRACTION

Citation Formats

Vasylechko, L., Senyshyn, A., Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt, Trots, D., Niewa, R., Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching, Schnelle, W., Knapp, M., and CELLS, POB 68, 08193, Barcelona. CeAlO{sub 3} and Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd) solid solutions: Crystal structure, thermal expansion and phase transitions. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2007.01.020.
Vasylechko, L., Senyshyn, A., Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt, Trots, D., Niewa, R., Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching, Schnelle, W., Knapp, M., & CELLS, POB 68, 08193, Barcelona. CeAlO{sub 3} and Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd) solid solutions: Crystal structure, thermal expansion and phase transitions. United States. doi:10.1016/j.jssc.2007.01.020.
Vasylechko, L., Senyshyn, A., Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt, Trots, D., Niewa, R., Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching, Schnelle, W., Knapp, M., and CELLS, POB 68, 08193, Barcelona. Sun . "CeAlO{sub 3} and Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd) solid solutions: Crystal structure, thermal expansion and phase transitions". United States. doi:10.1016/j.jssc.2007.01.020.
@article{osti_21015775,
title = {CeAlO{sub 3} and Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd) solid solutions: Crystal structure, thermal expansion and phase transitions},
author = {Vasylechko, L. and Senyshyn, A. and Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt and Trots, D. and Niewa, R. and Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching and Schnelle, W. and Knapp, M. and CELLS, POB 68, 08193, Barcelona},
abstractNote = {The crystal structures of CeAlO{sub 3} and the solid solutions Ce{sub 1-} {sub x}R{sub x} AlO{sub 3} (R=La, Nd), and their thermal behaviour in a wide temperature range of 12-1200 K have been precisely determined by means of in situ high-resolution X-ray powder diffraction technique applying synchrotron radiation, thermal analysis and magnetic measurements. The unique sequence of the reversible phase transitions I4/mcm{r_reversible}Imma{r_reversible}R3-barc{r_reversible}Pm3-barm has been detected in CeAlO{sub 3} and solid solutions formed in the pseudo-binary system CeAlO{sub 3}-LaAlO{sub 3}. In the Ce{sub 1-} {sub x} Nd {sub x} AlO{sub 3} system, the samples with x=0.3 and 0.5 compositions undergo three phase transformations I2/m{r_reversible}Imma{r_reversible}R3-barc{r_reversible}Pm3-barm, whereas for the Ce-rich sample Ce{sub 0.9}Nd{sub 0.1}AlO{sub 3} four successive transitions are observed: I4/mcm{r_reversible}I2/m{r_reversible}Imma{r_reversible}R3-barc{r_reversible}Pm3-barm. = Crystal structure parameters of all structural polymorphs of CeAlO{sub 3} and solid solutions based on them as well as their thermal evolution are reported. Based on in situ powder diffraction and DTA/DSC data, the phase diagrams of the pseudo-binary systems CeAlO{sub 3}-LaAlO{sub 3} and CeAlO{sub 3}-NdAlO{sub 3} are constructed together with a combined phase diagram, where the transition temperatures are presented as a function of the average radius of rare-earth cations. - Graphical abstract: Combined phase diagram of the CeAlO{sub 3}-LaAlO{sub 3} and CeAlO{sub 3}-NdAlO{sub 3} systems, where the transition temperatures are presented as a function of the average radius of rare-earth cations. The letters indicate L iquid, C ubic, R hombohedral, O rthorhombic, M onoclinic and T etragonal phase fields.},
doi = {10.1016/j.jssc.2007.01.020},
journal = {Journal of Solid State Chemistry},
number = 4,
volume = 180,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • Compositionally homogeneous solid solutions of formula R[sub x]Ba[sub 1-x]TiO[sub 3[minus][delta]] (where R = La, Nd; 0 [<=] x [<=] 1) have been prepared by the dc arc-melting method. The La system showed a negative deviation from Vegard's Law due to BaO deficiencies, whereas the members of the Nd series were stoichiometric and showed a linear relationship between x and the lattice constant [alpha]. Single-phase oxygen deficient cubic Y[sub x]Ba[sub 1-x]TiO[sub 3[minus][delta]] phases were obtained (where O [<=] x [<=] 0.4 and O < [delta] [<=] 0.15). Two compositionally dependent phase transitions occur in the La and Nd systems: tetragonal (P4mm)-to-cubicmore » (Pm3m) at very low values of x (0.05) which is second order and cubic (Pm3m)-to-orthorhombic (Pbnm) at high values of x which appears to be first order. HREM and electron diffraction studies showed no evidence for A-site ordering, microdomain ordering, or superstructure formation in the cubic regions. Four-probe resistivity measurements showed metallic conductivities for a majority of the samples between R[sub 300] and 4 K with R[sub 300] [approx] 10[sup [minus]2][minus]10[sup [minus]4] [Omega]cm. Metallic conductivity correlates with the perovskite tolerance factor [t=(r[sub A] + r[sub O])] and occurs when 0.93 < t < 1.02 with semiconducting or insulating behavior occurring outside this range. Superconductivity was not observed above 4 K in any of the samples. The effective magnetic moments of the Nd[sup 3+] ions in the Nd[sub x]Ba[sub 1-x]TiO[sub 3] phases (ca. 3.3 [mu][sub B]) for x [<=] 0.9 were close to the free ion value (3.62[mu][sub B]). Electron localization is discussed in terms of structural parameters and electronic effects. 26 refs., 8 figs., 5 tabs.« less
  • Investigations on phase relationships and crystal structures have been conducted on several ternary rare-earth titanium antimonide systems. The isothermal cross-sections of the ternary RE-Ti-Sb systems containing a representative early (RE=La) and late rare-earth element (RE=Er) have been constructed at 800 deg. C. In the La-Ti-Sb system, the previously known compound La{sub 3}TiSb{sub 5} was confirmed and the new compound La{sub 2}Ti{sub 7}Sb{sub 12} (own type, Cmmm, Z=2, a=10.5446(10) A, b=20.768(2) A, and c=4.4344(4) A) was discovered. In the Er-Ti-Sb system, no ternary compounds were found. The structure of La{sub 2}Ti{sub 7}Sb{sub 12} consists of a complex arrangement of TiSb{sub 6}more » octahedra and disordered fragments of homoatomic Sb assemblies, generating a three-dimensional framework in which La atoms reside. Other early rare-earth elements (RE=Ce, Pr, Nd) can be substituted in this structure type. Attempts to prepare crystals in these systems through use of a tin flux resulted in the discovery of a new Sn-containing pseudoternary phase RETi{sub 3}(Sn{sub x}Sb{sub 1-x}){sub 4} for RE=Nd, Sm (own type, Fmmm, Z=8; a=5.7806(4) A, b=10.0846(7) A, and c=24.2260(16) A for NdTi{sub 3}(Sn{sub 0.1}Sb{sub 0.9}){sub 4}; a=5.7590(4) A, b=10.0686(6) A, and c=24.1167(14) A for SmTi{sub 3}(Sn{sub 0.1}Sb{sub 0.9}){sub 4}). Its structure consists of double-layer slabs of Ti-centred octahedra stacked alternately with nets of the RE atoms; the Ti atoms are arranged in kagome nets. - Graphical abstract: La{sub 2}Ti{sub 7}Sb{sub 12} contains sectioned layers consisting of Ti-centred octahedra linked by corner- and face-sharing.« less
  • Crystals of nonstoichiometric phases Sr{sub 1-x}R{sub x}F{sub 2+x} (R are 14 rare-earth elements) and the ordered phase Sr{sub 4}Lu{sub 3}F{sub 17} with a trigonally distorted fluorite lattice were grown by the Bridgman method. Ten of 26 Sr{sub 1-} {sub x}R{sub x}F{sub 2+x} crystals, where R = La-Ho or Y, melt congruently. The isoconcentration series Sr{sub 0.90}R{sub 0.10}F{sub 2.10} includes four crystals with R = Er-Lu. The compositions corresponding to the maxima for the latter crystals were not determined. The concentration series, in which the mole fraction of RF{sub 3} varies from 10 to 50 mol %, were obtained for themore » crystals with R = La, Nd, and Gd. Most of the crystals are of good optical quality. To evaluate the composition changes in the course of crystal growth, the cubic unit-cell parameters were determined by X-ray powder diffraction. The line-broadening analysis revealed a nonmonotonic change of microdistortions as regards both the rare-earth content and rare-earth series. The changes in the lattice parameters and the congruent-melting points of the Sr{sub 1-x}R{sub x}F{sub 2+x} phases in the rare-earth series reflect the morphotropic transitions in the series of pure RF{sub 3} despite the fact that SrF{sub 2} dominates in nonstoichiometric fluorite crystals.« less
  • As-grown Cd{sub 0.9}R{sub 0.1}F{sub 2.1} (R = La-Nd) crystals were assigned to the CaF{sub 2} structure type and their structure was determined by X-ray diffraction. A new octacubic cluster of structural defects in Cd{sub 0.9}R{sub 0.1}F{sub 2.1} phases is proposed. The changes in the anionic motif of the Cd{sub 0.9}R{sub 0.1}F{sub 2.1} phase can be explained as a result of the formation of tetrahedral [Cd{sub 4-n}R{sub n}F{sub 26}] and inverse octacubic [Cd{sub 14-n}R{sub n}F{sub 68}] clusters with, respectively, tetrahedral and cuboctahedral anionic groups as cores. It is established that fluctuations of the La concentration in the cross section of amore » Cd{sub 0.9}La{sub 0.1}F{sub 2.1} crystal boule do not exceed 2.7%.« less
  • Phosphates R{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} (R = Nd, Eu, or Er) and Er{sub 0.33(1–x)}Zr{sub 0.25}Zr{sub 2}(PO{sub 4}){sub 3} (x = 0, 0.25, 0.5, 0.75, 1.0) of the NaZr{sub 2}(PO{sub 4}){sub 3} family have been synthesized and investigated by high-temperature X-ray diffraction. The crystallochemical approach is used to obtain compounds with expected small and controllable thermal-expansion parameters. Phosphates with close-to-zero thermal-expansion parameters, including those with low thermal-expansion anisotropy, have been obtained: Nd{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} with α{sub a} =–2.21 × 10{sup −6} °C{sup −1}, α{sub c} = 0.81 × 10{sup −6} °C{sup −1}, and Δα = 3.02 × 10{supmore » −6} °C{sup –1} and Er{sub 0.08}Zr{sub 0.19}Zr{sub 2}(PO{sub 4}){sub 3} with α{sub a} =–1.86 × 10{sup −6} °C{sup −1}, α{sub c} = 1.73 × 10{sup −6} °C{sup −1}, and Δα = 3.58 × 10{sup −6} °C{sup −1}.« less