Synthesis and characterisation of La0.4Ba0.6Ti0.6RE0.4O3 (where RE=Y, Yb) ceramics

Feteira, Antônio; Elsebrock, R.; Dias, Anderson; Moreira, R. L.; Lanagan, Michael T.; Sinclair, Derek C.

doi:10.1016/j.jeurceramsoc.2005.09.095

Cited by 15 publications

(9 citation statements)

References 14 publications

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“…The nearest splitting for the 722 cm −1 band like BET was observed in Ba(Ti 1 − x Zr x )O 3 ceramics, in which this band splits into two bands at 720 and 780 cm −1 owing to heavy Zr substitution ( x ≥ 0.15) and the other conventional RS persist . Feteira et al attributed two bands at 713 cm −1 and 780 cm −1 observed for La 0.4 Ba 0.6 Ti 0.6 RE 0.4 O 3 (where RE = Y, Yb) ceramics to E oxygen mode and A 1 symmetric ‘breathing’ of BO 6 octahedrons, respectively, owing to a mass effect . However, the large increase in intensity of the 720/780 cm −1 peaks resembling BET cannot be obtained by these researchers …”

Section: Discussionmentioning

confidence: 91%

“…Feteira et al attributed two bands at 713 cm −1 and 780 cm −1 observed for La 0.4 Ba 0.6 Ti 0.6 RE 0.4 O 3 (where RE = Y, Yb) ceramics to E oxygen mode and A 1 symmetric ‘breathing’ of BO 6 octahedrons, respectively, owing to a mass effect . However, the large increase in intensity of the 720/780 cm −1 peaks resembling BET cannot be obtained by these researchers …”

Section: Discussionmentioning

confidence: 94%

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Abnormal Raman spectra in Er‐doped BaTiO₃ ceramics

Cheng

Sun

et al. 2014

J Raman Spectroscopy

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Greatly enhanced and abnormal Raman spectra were discovered in the nominal (Ba1 − xErx)Ti1 − x/4O3 (x = 0.01) (BET) ceramic for the first time and investigated in relation to the site occupations of Er3+ ions. BaTiO3 doped with Ti‐site Er3+ mainly exhibited the common Raman phonon modes of the tetragonal BaTiO3. Er3+ ions substituted for Ba sites are responsible for the abnormal Raman spectra, but the formation of ErBa•−ErTi' defect complexes will decrease spectral intensity. A large increase in intensity showed a hundredfold selectivity for Ba‐site Er3+ ions over Ti‐site Er3+ ions. A strong EPR signal at g = 1.974 associated with ionized Ba vacancy defects appeared in BET, and the defect chemistry study indicated that the real formula of BET is expressed by (Ba1 − xEr3x/4)(Ti1 − x/4Erx/4)O3. These abnormal Raman signals were verified to originate from a fluorescent effect corresponding to 4S3/2→4I15/2 transition of Ba‐site Er3+ ions. The fluorescent signals were so intense that they overwhelmed the traditional Raman spectra of BaTiO3. The significance is that the abnormal Raman spectra may act as a probe for the Ba‐site Er3+ occupation in BaTiO3 co‐doped with Er3+ and other dopants. A new broad EPR signal at g = 2.23 was discovered, which originated from Er3+ Kramers ions. Copyright © 2014 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 94%

Abnormal Raman spectra in Er‐doped BaTiO₃ ceramics

Cheng

Sun

et al. 2014

J Raman Spectroscopy

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“…Later, Feteira et al 17 observed that double doped-BT ceramics with relaxor-type behavior can exhibit high tunability but they also noted high dielectric losses in the MW regime, thus, precluding their use in high frequency applications. In particular, Feteira et al 22 observed La 0.4 Ba 0.6 Ti 0.6 Y 0.4 O 3 ceramics to exhibit r = 57, quality factor ͑Q ϫ f r , where Q = 1 / tan ␦ and f r is the resonant frequency͒ of ϳ750 GHz and temperature coefficient of the resonant frequency ͑TCF͒ ϳ+12 ppm/ K, and BaTi 0.4 Ga 0.3 Nb 0.3 O 3 ceramics to exhibit r ϳ 66, Q ϫ f r ϳ 3720 GHz and TCFϳ +72 ppm/ K. 19 The origin͑s͒ of exceptionally high MW dielectric losses in heavily cosubstituted BT ceramics in comparison with CaTiO 3 -based ceramics ͑e.g., Ca 0.7 Nd 0.3 Ti 0.7 Al 0.3 O 3 , exhibits r ϳ 45 and Q ϫ f r ϳ 45 000 GHz͒ ͑Ref. [19][20][21] Invariably, these materials exhibit temperature stable permittivity behavior but the dielectric losses at MW frequencies are too high for technological applications.…”

Section: Introductionmentioning

confidence: 99%

Effects of average and local structure on the dielectric behavior of (1−x)BaTiO3–xLaYO3 (≤x≤0.40) ceramics

Feteira

Sinclair

Lanagan

2010

Journal of Applied Physics

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Articles you may be interested inEvolution of structure, dielectric properties, and re-entrant relaxor behavior in 0.25, 0.5) tungsten bronze ceramics J. Appl. Phys. 114, 044106 (2013); 10.1063/1.4816480 Re-entrant relaxor behavior of Ba5RTi3Nb7O30 (R=La, Nd, Sm) tungsten bronze ceramics Appl. Phys. Lett. 102, 112912 (2013); 10.1063/1.4796135Local order and electronic structure of Pb1−xLaxZr0.40Ti0.60O3 materials and its relation with ferroelectric propertiesThe dielectric properties of dense ceramics of ͑1−x͒BaTiO 3 -xLaYO 3 ͑LBTY͒ ͑0 Յ x Յ 0.40͒ were characterized in the temperature range 10 to 450 K. The Curie temperature, T c , of LBTY ceramics decreases at a rate of Ϫ23 K/at. % ͑La,Y͒ for x Ͻ 0.10 but increases at +7 K / at. % ͑La,Y͒ for x Ն 0.20. The room temperature relative permittivity, RT , decreases from ϳ2000 for x = 0.10 to ϳ57 for x = 0.40. This variation is accompanied by a substantial reduction in the temperature dependence of the relative permittivity, r , and also by the emergence of relaxor ferroelectric-like behavior at x Ͼ 0.05. The gradual transition from a classical ferroelectric to a relaxor-type response results from disruption of the long-range ferroelectric order, believed to be caused by a nanoclustering phenomenon. x = 0.10 exhibits all the characteristic features of a relaxor-ferroelectric, i.e., r decreases and tan ␦ increases with increasing frequency. For x Ͼ 0.20 the relaxor behavior becomes progressively more subtle, suggesting a weaker coupling between the polar nanoregions. The poor microwave dielectric properties of LBTY ceramics, in particular for x = 0.40, which exhibit RT ϳ 57 and a quality factor of ϳ755 GHz are attributed to phase separation on the nanometer scale.

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“…Alkaline‐earth titanates (ATiO 3 ) and zirconates (AZrO 3 ) (A=Pb, Ba, Sr, and Ca) have played a crucial role in the development of near‐zero τ f MW dielectric ceramics 7,9–19 . Nevertheless, these two families of simple perovskites exhibit dramatically different properties as indicated in Table I.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure and Microwave Dielectric Properties of Alkaline‐Earth Hafnates, AHfO₃ (A=Ba, Sr, Ca)

Feteira

Sinclair

Rajab

et al. 2008

Journal of the American Ceramic Society

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The crystal structure and microwave (MW) dielectric properties of AHfO3 (A=Ba, Sr, and Ca) ceramics prepared by the solid‐state route have been investigated. X‐ray and electron diffraction show BaHfO3 to be an untilted cubic perovskite (a0a0a0, space group ), whereas SrHfO3 and CaHfO3 are both orthorhombically distorted perovskites (a−b+a−, space group Pnma). AHfO3 ceramics with a relative density ∼90% of the theoretical X‐ray density and microstructures consisting of randomly oriented equiaxed grains were prepared by firing at 1750°C for 6 h. Conventional transmission electron microscopy reveals the occurrence of long parallel ferroelastic domains in the subgrain microstructure of CaHfO3 and SrHfO3. At room temperature and MW frequencies, AHfO3 ceramics, where A=Ba, Sr, and Ca, have ɛr∼24.2, Q×fr∼14 250 GHz (at 8.9 GHz) and τf∼+111 ppm/K; ɛr∼23.5, Q×fr∼33 534 GHz (at 9.3 GHz), and τf∼−63 ppm/K; and ɛr∼21.4, Q×fr∼15 950 GHz (at 8.9 GHz), and τf∼−33 ppm/K, respectively. The ion polarizability for Hf4+ in a cubic perovskite environment is calculated to be 3.32 Å3, whereas in a noncubic environment it increases to 4.36–4.47 Å3. Finally, the dielectric properties of AHfO3 (A=Ba, Sr, and Ca) are compared with their titanate and zirconate counterparts.

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Synthesis and characterisation of La0.4Ba0.6Ti0.6RE0.4O3 (where RE=Y, Yb) ceramics

Cited by 15 publications

References 14 publications

Abnormal Raman spectra in Er‐doped BaTiO₃ ceramics

Abnormal Raman spectra in Er‐doped BaTiO₃ ceramics

Effects of average and local structure on the dielectric behavior of (1−x)BaTiO3–xLaYO3 (≤x≤0.40) ceramics

Crystal Structure and Microwave Dielectric Properties of Alkaline‐Earth Hafnates, AHfO₃ (A=Ba, Sr, Ca)

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Synthesis and characterisation of La0.4Ba0.6Ti0.6RE0.4O3 (where RE=Y, Yb) ceramics

Cited by 15 publications

References 14 publications

Abnormal Raman spectra in Er‐doped BaTiO3 ceramics

Abnormal Raman spectra in Er‐doped BaTiO3 ceramics

Effects of average and local structure on the dielectric behavior of (1−x)BaTiO3–xLaYO3 (≤x≤0.40) ceramics

Crystal Structure and Microwave Dielectric Properties of Alkaline‐Earth Hafnates, AHfO3 (A=Ba, Sr, Ca)

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Product

Resources

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Abnormal Raman spectra in Er‐doped BaTiO₃ ceramics

Abnormal Raman spectra in Er‐doped BaTiO₃ ceramics

Crystal Structure and Microwave Dielectric Properties of Alkaline‐Earth Hafnates, AHfO₃ (A=Ba, Sr, Ca)