| Records |
| Author |
Lazoryak, B.I.; Baryshnikova, O.V.; Stefanovich, S.Y.; Malakho, A.P.; Morozov, V.A.; Belik, A.A.; Leonidov, I.A.; Leonidova, O.N.; Van Tendeloo, G. |
| Title |
Ferroelectric and ionic-conductive properties of nonlinear-optical vanadate, Ca9Bi(VO4)7 |
Type |
A1 Journal article |
| Year |
2003 |
Publication |
Chemistry of materials |
Abbreviated Journal |
Chem Mater |
| Volume |
15 |
Issue |
15 |
Pages |
3003-3010 |
| Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
| Abstract |
Structural, chemical, and physical properties of whitlockite-type Ca9Bi(VO4)(7) were studied by X-ray powder diffraction (XRD), electron diffraction (ED), second-harmonic generation (SHG), thermogravimetry, differential scanning calorimetry, dielectric, and electrical-conductivity measurements. A new phase-transition of the ferroelectric type was found in Ca9Bi(VO4)(7) with a transition temperature, T-c of 1053 +/- 3 K. The polar phase, beta-Ca9Bi(VO4)(7), is stable below T-c down to at least 160 K. The centrosymmetric beta'-phase is stable above T-c up to 1273 +/- 5 K. Above 1273 K, it decomposes to give BiVO4 and whitlockite-type solid solutions of Ca9+1.5xBi1-x(VO4)(7). The beta<---->beta' phase transition is reversible and of second order. Electrical conductivity of beta'-Ca9Bi(VO4)(7) is rather high (sigma = 0.6 x 10(-3) S/cm at 1200 K) and obeys the Arrhenius law with an activation energy of 1.0 eV. Structure parameters of Ca9Bi(VO4)(7) are refined by the Rietveld method from XRD data measured at room temperature (space group R3c; Z = 6; a = 10.8992(1) Angstrom, c = 38.1192(4) Angstrom, and V = 3921.6(1) Angstrom(3); R-wp = 3.06% and R-p = 2.36%). Bi3+ ions together with Ca2+ ions are statistically distributed among the M1, M2, M3, and M5 sites. Ca9Bi(VO4)(7) has a SHG efficiency of about 140 times that of quartz. Through the powder SHG measurements, we estimated the nonlinear optical susceptibility, Digital, at about 6.1-7.2 pm/V. This value for Ca9Bi(VO4)(7) is comparable with that for known nonlinear optical materials such as LiNbO3 and LiTaO3. |
| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication  |
Washington, D.C. |
Editor |
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| Language |
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Wos |
000184379900024 |
Publication Date |
2003-07-22 |
| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
0897-4756;1520-5002; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
| Impact Factor |
9.466 |
Times cited |
51 |
Open Access |
|
| Notes |
Iup V-1; Dwtc |
Approved |
Most recent IF: 9.466; 2003 IF: 4.374 |
| Call Number |
UA @ lucian @ c:irua:103284 |
Serial |
1179 |
| Permanent link to this record |
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| Author |
Morozov, V.A.; Bertha, A.; Meert, K.W.; Van Rompaey, S.; Batuk, D.; Martinez, G.T.; Van Aert, S.; Smet, P.F.; Raskina, M.V.; Poelman, D.; Abakumov, A.M.; Hadermann, J.; |
| Title |
Incommensurate modulation and luminescence in the CaGd2(1-x)Eu2x(MoO4)4(1-y)(WO)4y (0\leq x\leq1, 0\leq y\leq1) red phosphors |
Type |
A1 Journal article |
| Year |
2013 |
Publication |
Chemistry of materials |
Abbreviated Journal |
Chem Mater |
| Volume |
25 |
Issue |
21 |
Pages |
4387-4395 |
| Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
| Abstract |
Scheelite related compounds (A',A '') [(B',B '')O-4], with B', B '' = W and/or Mo are promising new light-emitting materials for photonic applications, including phosphor converted LEDs (light-emitting diodes). In this paper, the creation and ordering of A-cation vacancies and the effect of cation substitutions in the scheelite-type framework are investigated as a factor for controlling the scheelite-type structure and luminescent properties. CaGd2(1-x)Eu2x(MoO4)(4(1-y))(WO4)(4y) (0 <= x <= 1, 0 <= y <= 1) solid solutions with scheelite-type structure were synthesized by a solid state method, and their structures were investigated using a combination of transmission electron microscopy techniques and powder X-ray diffraction. Within this series all complex molybdenum oxides have (3 + 2)D incommensurately modulated structures with superspace group I4(1)/a(alpha,beta,0)00(-beta,alpha,0)00, while the structures of all tungstates are (3 + 1)D incommensurately modulated with superspace group I2/b(alpha beta 0)00. In both cases the modulation arises because of cation-vacancy ordering at the A site. The prominent structural motif is formed by columns of A-site vacancies running along the c-axis. These vacant columns occur in rows of two or three aligned along the [110] direction of the scheelite subcell. The replacement of the smaller Gd3+ by the larger Eu3+ at the A-sublattice does not affect the nature of the incommensurate modulation, but an increasing replacement of Mo6+ by W6+ switches the modulation from (3 + 2)D to (3 + 1)D regime. Thus, these solid solutions can be considered as a model system where the incommensurate modulation can be monitored as a function of cation nature while the number of cation vacancies at the A sites remain constant upon the isovalent cation replacement. All compounds' luminescent properties were measured, and the optical properties were related to the structural properties of the materials. CaGd2(1-x)(MoO4)(4(1-y))(WO4)(4y) phosphors emit intense red light dominated by the D-5(0)-F-7(2) transition at 612 nm, along with other transitions from the D-5(1) and D-5(0) excited states. The intensity of the 5D0-7F2 transition reaches a maximum at x = 0.5 for y = 0 and 1. |
| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Washington, D.C. |
Editor |
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| Language |
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Wos |
000327045000030 |
Publication Date |
2013-09-24 |
| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
0897-4756;1520-5002; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
| Impact Factor |
9.466 |
Times cited |
63 |
Open Access |
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| Notes |
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Approved |
Most recent IF: 9.466; 2013 IF: 8.535 |
| Call Number |
UA @ lucian @ c:irua:112776 |
Serial |
1594 |
| Permanent link to this record |
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| Author |
Morozov, V.A.; Arakcheeva, A.V.; Chapuis, G.; Guiblin, N.; Rossell, M.D.; Van Tendeloo, G. |
| Title |
KNd(MoO4)2: a new incommensurate modulated structure in the scheelite family |
Type |
A1 Journal article |
| Year |
2006 |
Publication |
Chemistry of materials |
Abbreviated Journal |
Chem Mater |
| Volume |
18 |
Issue |
17 |
Pages |
4075-4082 |
| Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
| Abstract |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Washington, D.C. |
Editor |
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| Language |
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Wos |
000239758300022 |
Publication Date |
2006-07-28 |
| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
0897-4756;1520-5002; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
| Impact Factor |
9.466 |
Times cited |
46 |
Open Access |
|
| Notes |
Iap V-1 |
Approved |
Most recent IF: 9.466; 2006 IF: 5.104 |
| Call Number |
UA @ lucian @ c:irua:60688 |
Serial |
3538 |
| Permanent link to this record |
