Characterization and Rietveld Refinement of A-site deficient Lanthanum doped Barium Titanate

doi:10.1016/j.jallcom.2013.06.104

Journal of Alloys and Compounds

Volume 579, 5 December 2013, Pages 473-484

https://doi.org/10.1016/j.jallcom.2013.06.104 Get rights and content

Highlights

•
Ba_1-xLa_2x/3TiO₃ ceramics have been prepared using standard SSR route.
•
Compositionally induced structural transition at 6% La substitution.
•
Onset of relaxor behavior traced at 8% La substituted composition.
•
Presence of shallow defects showed blue luminescence.
•
Optical band gap reduced with La concentration.

Abstract

Ba₁₋_xLa₂_x_/3TiO₃ (0.00 ⩽ x ⩽ 0.10, in a step of 0.02) ceramics have been prepared through solid state reaction route. Structural studies suggested a transition in phase from tetragonal to cubic symmetry with increase in Lanthanum content. Rietveld Refinement technique employed for investigation confirmed the same. Photoluminescence study revealed introduction of structural disorder by means of A-site vacancies and displacement of M–O bond leading to shallow defects. Optical band gap value calculated from UV–Vis spectra decreased with increase in La concentration. A drastic decrease in grain size of undoped BT was observed with introduction of La through Scanning Electron Micrographs. Dielectric studies were performed and a gradual decrease in the Curie temperature with increase in La content in coherence with structural studies was observed along with pinching effect. Normal ferroelectric character was obtained for the composition x = 0.00 to x = 0.06 while relaxor like behavior was observed for composition x ⩾ 0.08. The composition x = 0.10 made a good Vogel–Fulcher fit. Inhomogeneity induced in the BT lattice due to 8% La doping is strong enough to make an onset of such behavior. P $\sim$ E hysteresis loop showed a regular decrease in remnant polarization and coercive field featuring similar relaxor like behavior.

Introduction

Barium Titanate (BT) has been widely investigated and has experienced a renaissance in the past decade due to its long range of applications. It has its application in multilayer ceramic capacitors, electro mechanical system, electro optical system, pyroelectric detectors, piezoelectric actuators, MEMS, FeRAM devices, etc. [1].

Doped BT with rare earth elements has been an upcoming area of research for the past few decades and among them Lanthanum (La) has been a material of great importance. La behaves as a donor as it occupies the Ba site. Though undoped BT is electrically insulating, electrical resistance can be controlled through La doping. Even PTCR effect has been shown by donor doped BT [2], [3]. Rare earth elements especially La doped BT has been mostly popular as a dielectric material in Ni-MLCC as these are effective in V_o trapping and controlling the microstructure enhancing the reliability [4], [5], [6]. Solubility of La into the BT lattice has been quite high as compared to other rare earth elements resulting in a change in symmetry from tetragonal to cubic and a change in grain size which is again of importance [3], [7], [8]. Xinle et al. have also reported the same [9]. Beside this Aliouane et al. had been able to obtain relaxor behavior for more than 10% doping in charge compensated La doped BT. Structural distortion induced by La ions has been considered to be the reason behind [10].

Thus it has been well established that La doped BT is a perfect material to be used as a dielectric in capacitors with high dielectric constant, a stable capacitance value, long service life, low-loss factor, high insulation resistance, reduced Curie temperature, low voltage dependence and low temperature dependence of the dielectric constant over a wide temperature range [2], [3], [4], [5], [6], [7], [8], [9], [10], [11].

BT has a perovskite structure (ABO₃) where Ba occupies the A site and Ti the B site. La is incorporated at the A site where it behaves as a donor according to the equation: ${Ba}^{2 +} \to {La}^{3 +} + e$

Creation of oxygen vacancies also takes place leading to semiconductive behavior, according to the equation: $O^{2 -} \to 1 / 2 O_{2} + 2 e$

The effect of Ln-substitution for Ba-ion can be expressed by Kröger–Vink notation as: $BaO + {Ln}_{2} O_{3} \to {Ba}_{Ba} + 2 {Ln}_{Ba} + V_{Ba}^{″} + 4 O_{O}$

Since the substitution at the A site is off valent (Ba²⁺ being substituted by smaller La³⁺), so to obtain charge neutrality vacancy is created. Eq. (3) implies that for every two rare earth cation substitution at the A-site, three alkaline cations gets replaced creating one positively double charge vacancy, provided the charges are to be taken to the perfect lattice. This number of vacancy increases with increase in doping concentration [12], [13].

La doped BT ceramics were prepared according to the equation: $(1 - x) {BaCO}_{3} + {TiO}_{2} + (x / 3) {La}_{2} O_{3} \to {Ba}_{1 - x} {La}_{2 x / 3} {TiO}_{3} + {CO}_{2}$ where x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10.

Excluding the composition x = 0.00, all the other compositions are non-stoichiometric, exhibiting A-site deficient perovskite type solid solutions according to the structural formula:

Ba₁₋_xLa₂_x_/3□_x_/3TiO₃, where □ denotes A-site vacancy in the perovskite structure [10].

Though much work has been done in the past years in A-site and B-site doping of BT there is no clear picture about the various doping mechanism and defect chemistry associated with the various types of doping. In particular the doping of La in BT has been widely debated. This attracted us towards this zone of research with a core aim to justify charge compensated A-site deficient Lanthanum doped Barium Titanate in all possible respect.

Section snippets

Experimental procedure

Ba₁₋_xLa₂_x_/3TiO₃ (0.00 ⩽ x ⩽ 0.10) ceramics were prepared through solid state reaction technique from reagents BaCO₃ (99% Pure, Merck, India Ltd.), TiO₂ (99% Pure, Merck, India Ltd.) and La₂O₃ (99.99% Pure, Sigma–Aldrich, USA). Powders were mixed in an appropriate amount and grinded with distilled water in an agate mortar. The homogeneous mixture was milled in a FRITSCH “Pulverisette 5” planetary mill for 10 h with Zirconium balls (5 mm diameter) and then heated at 1200 °C for 12 h. The process was

Results and discussion

Fig. 1 shows the XRD pattern of Ba₁₋_xLa₂_x_/3TiO₃ ceramic powders calcined at 1400 °C for 4 h. All the compositions show the reflections of single phase perovskite structure. The diffraction pattern of all composition within the 2θ range of 44°–46° is shown in a magnified scale for clarity. The presence of (0 0 2), (2 0 0) peaks suggests tetragonal symmetry at room temperature for the compositions x ⩽ 0.04. A Gaussian fit showing the presence of both the peaks is shown in inset. However merging of both

Conclusions

Ba₁₋_xLa₂_x_/3TiO₃ (x = 0.02, 0.04, 0.06, 0.08, and 0.10) were prepared by solid state reaction route. Rietveld Refinement confirm a compositionally induced phase transition from tetragonal to cubic symmetry at the composition x = 0.06. The same is supported through FTIR, Raman spectroscopy and temperature dependent dielectric study. FTIR study reveal distortion in the TiO₆ octahedra and increase in Ti–O bond strength due to La substitution. Decrease in intensity, followed by a disappearance of the

References (58)

H. Kishi et al.
Occupational sites and dielectric properties of rare-earth and Mn substituted BaTiO₃
J. Eur. Ceram. Soc.
(2001)
H. Kishi et al.
The effect of rare-earth (La, Sm, Dy, Ho and Er) and Mg on the microstructure in BaTiO₃
J. Eur. Ceram. Soc.
(1999)
M.T. Buscaglia et al.
Influence of foreign ions on the crystal structure of BaTiO₃
J. Eur. Ceram. Soc.
(2000)
K. Watanabe et al.
Solubility of La–Mg and La–Al in BaTiO₃
Solid State Ionics
(1998)
Z. Xinle et al.
Preparation and characterization on nano-sized barium titanate powder doped with lanthanum by sol–gel process
J. Rare Earths
(2006)
F.D. Morrison et al.
Doping mechanisms and electrical properties of La-doped BaTiO₃ ceramics
Int. J. Inorg. Mater.
(2001)
Z. Yu et al.
Dielectric properties of Ba(Ti₁₋_xZr_x)O₃
Mater. Lett.
(2007)
C. Ostos et al.
Synthesis and characterization of A-site deficient rare-earth doped BaZr_xTi₁₋_xO₃ perovskite-type compounds
Solid State Sci.
(2009)
D. Wang et al.
Hydrothermal synthesis of perovskite-type solid solution of (1 − x)BaTiO₃⋅xLa_2/3TiO₃
Solid State Ionics
(2002)
Y. Liu et al.
Microwave absorption properties of La doped barium titanate in X-band
J. Alloys Comp.
(2009)

M. Ganguly et al.

Characterization of A-site deficient samarium doped barium titanate

Physica B

(2013)

X. Chou et al.

Relaxor behavior and dielectric properties of La₂O₃-doped barium zirconium titanate ceramics for tunable device applications

Mater. Chem. Phys.

(2008)

T. Badapanda et al.

Rietveld Refinement, microstructure, conductivity and impedance properties of Ba[Zr_0.25Ti_0.75]O₃ ceramic

Curr. Appl. Phys.

(2011)

J. Ravez et al.

Some solid state chemistry aspects of lead-free relaxor ferroelectrics

J. Solid State Chem.

(2001)

M. Ganguly et al.

Structural, dielectric and electrical properties of BaFe_0.5Nb_0.5O₃ ceramic prepared by solid-state reaction technique

Mater. Chem. Phys.

(2011)

T. Sahoo et al.

Microstructural and photo luminescence studies on hydrothermally synthesized Ce-doped barium titanate nanocrystals

Mater. Sci. Eng. B

(2006)

E. Orhan et al.

A DFT rationalization of the room temperature photoluminescence of Li₂TiSiO₅

Chem. Phys. Lett.

(2004)

S.K. Rout et al.

Photoluminescence property of Ba(Zr_0.25Ti_0.75)O₃ powders prepared by solid state reaction and polymeric precursor method

Physica B

(2009)

A.J. Moulson et al.

Electroceramic: Materials Properties and Applications

(1990)

Y. Wenhu et al.

Study of reoxidation in heavily La-doped barium titanate ceramics

J. Phys.: Conf. Ser.

(2009)

D. Makovec et al.

Microstructural changes during the reduction/reoxidation process in donor doped BaTiO₃ ceramics

J. Am. Ceram. Soc.

(2000)

A. Honda et al.

Theoretical study on interactions between oxygen vacancy and doped rare-earth elements in barium titanate

Jap. J. Appl. Phys.

(2011)

K. Alioune et al.

Study of new relaxor materials in BaTiO₃–BaZrO₃–La_2/3TiO₃ system

Solid State Sci.

(2005)

Z. Valdez-Nava et al.

Colossal dielectric permittivity of BaTiO₃-based nanocrystalline ceramics sintered by spark plasma sintering

J. Electroceram.

(2009)

F.D. Morrison et al.

Electrical and structural properties of characteristics of lanthanum-doped barium titanate ceramics

J. Appl. Phys.

(1999)

C.H. Perry et al.

Infrared studies of perovskite titanates

Phys. Rev.

(1964)

R.A. Nyquist et al.

Infrared Spectra Inorganic Compounds

(1971)

X. Jin et al.

Investigation on FTIR spectra of barium calcium titanate ceramics

J. Electroceram.

(2009)

D. Sun et al.

Investigation on FTIR spectrum of barium titanate ceramics doped with alkali ions

Ferroelectrics

(2007)

Cited by (160)

Modification of structural, morphological, and dielectric properties of barium calcium titanate ceramics with yttrium addition
2024, Heliyon
Barium calcium titanate (BCT) ceramics with varying yttrium doping concentrations were fabricated using the solid-state compaction process to explore the attributes of dopants. (Ba_0.75Ca_0.25) TiO₃ and (Ba_0.75Ca_0.25) (Y_yTi_(1-y)) O₃ where, y = 0.00, 0.10, 0.15, and 0.20 ceramics were synthesized by pressing isostatically in pellet press apparatus, then sintered at 1250 °C with consequent cooling in furnace ambient. The structural, morphological, and dielectric properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and impedance spectroscopy interpretations, respectively. The XRD analysis revealed that the cubic BCT lattice was transformed into a tetragonal structure with Yttrium doping. Scanning electron microscopy (SEM) disclosed that yttrium doping countered the liquid phase formation of BCT as well as influenced grain development and microstructure, leading to the formation of distinct grain boundaries and improved densification. The average grain size (18–29 nm) of the Y-BCT increases as the doping level rises. At 60 Hz, it was reported that the dielectric constant obtained a maximum value of 70000 with a resistivity of 5 × 10⁸ Ώ-cm for y = 0.15. The manifestation of the secondary phase confirmed from XRD, allocating an easy path for oxygen migration, might be responsible for the rise in oxygen vacancy, higher leakage current, and dielectric loss for y = 0.01. Co-doping of calcium and yttrium in BCT ceramics has modified the basic structure and ameliorated composites' structural stability and dielectric characteristics. The optimized sample, upon demonstrating outstanding efficiency, ought to be employed for specific uses such as energy storage devices and capacitors.
Investigation of structural, electrical and optical properties of lanthanum and zirconium doped barium titanate ceramics
2023, Materials Science and Engineering: B
In this work, Ba_1-xLa_xTi _(1-y)-x/4Zr_yO₃ (x = 0.015, y = 0.15, 0.25, 0.35) ceramics were fabricated by solid-state sintering. The structural, dielectric, and optical properties were investigated. The samples exhibited a tetragonal structure that became somewhat deformed towards pseudocubicity with increasing zirconium content. The inclusion of lanthanum created titanium vacancies and impeded the growth of grains. In y = 0.15 (BLZT15) composition, the grain size is 0.49 μm. The substitution of zirconium increased density by 3.17 gcm⁻³ in y = 0.25 (BLZT25), hence accelerating domain wall motion and enhancing the dielectric constant. The highest value of dielectric constant and grain size for y = 0.25 (BLZT25) ceramics was determined to be ∼3200 and 0.65 μm respectively. With increasing Zr⁴⁺ content, the optical band gap was observed to decrease from 2.75 eV to 2.40 eV. Lanthanum and Zirconium doped barium titanate ceramics would be desirable materials for ceramic capacitors and electronic components.
Ultrahigh insulation resistivity potential under colossal permittivity SrTiO<inf>3</inf> based ceramics via controlling oxygen backfill
2023, Journal of Alloys and Compounds
Effects of annealing atmosphere on the dielectric properties of Sr_1-xEr_xTiO₃ ceramics (x = 0–0.014) were systematically investigated in this paper. In x = 0.012 ceramic samples annealed in air, the stable insulation resistivity of over 10⁹ Ω • cm (DC 0–150 V), the CP (16,635 @ 1 kHz, 16,822 @ 1 MHz), and the ultralow dielectric loss (0.006 @ 1 kHz, 0.02 @ 1 MHz) are achieved. Through a thorough examination of dielectric responses, X-ray photoelectron spectroscopy (XPS), UV–visible absorption spectrum, and complex impedance data, it is demonstrated that the defect dipoles [ ${Ti}_{Ti}^{'} - V_{O}^{··} - {Ti}_{Ti}^{'}]$ , $[{Er}_{Sr}^{\cdot} - {Ti}_{Ti}^{'}], [2 {Er}_{Ti}^{'} - V_{O}^{··}]$ , [ ${Ti}_{Ti}^{'} - V_{O}^{\cdot}]$ , [ ${Er}_{Ti}^{'} - V_{O}^{\cdot}]$ and ${[Er}_{Sr}^{\cdot} - {Er}_{Ti}^{'}]$ form in Sr_1-xEr_xTiO₃ (when x = 0.012) ceramic annealed under flowing air. We innovatively used variable temperature in situ resistance monitoring equipment to simulate the industrial environment, the insulating properties and the microscopic mechanism of oxygen vacancy diffusion of ceramics were investigated under different voltages and temperatures, which is of great significance to achieve more desirable colossal permittivity, ultra-low dielectric loss and insulation resistivity performance for real applications.
Exploring the coupling effect of ferromagnetic, Co<inf>0.8</inf>Zn<inf>0.2</inf>Fe<inf>2</inf>O<inf>4</inf> with the ferroelectric, Ba<inf>0.5</inf>La<inf>0.5</inf>TiO<inf>3</inf> at different concentrations in composite multiferroics
2023, Journal of Magnetism and Magnetic Materials
The solid-state reaction method is followed to fabricate multiferroic particulate composites, (1-x) Ba_0.5La_0.5TiO₃ + (x) Co_0.8Zn_0.2Fe₂O₄ (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0). X-ray diffraction patterns reflect the coexistence of the constituent phases in the composites after 4 h of sintering at 1200 °C. Cubic structures of both ferroelectric and ferrite phases confirmed from Rietveld refinement are distinctively dominant. The Fourier Transform Infrared (FTIR) spectrum confirms the characteristic vibration bonds of Co-ferrite, Zn-ferrite, and Ti-O. A slight variation of lattice parameters is observed with the increasing ferrite concentration. Bulk density reveals the inverse behavior of theoretical density. The obtained average grain size varies from 1.308 µm to 3.046 µm. All the composites have good ferromagnetic properties confirmed by hysteresis loops. The coercive field at x = 0.5 is 297.98 Oe, dramatically higher than other concentrations. The real part of permeability ( $μ_{i}^{'}$ ) gradually increases with increasing ferrite content as per the sum rule of the mixture. To investigate the electric properties of the samples, the dielectric constant ( $ε^{'}$ ) and loss tangent (tanδ) are measured in the frequency range of 100 Hz to 100 MHz. The dielectric constant ( $ε^{'}$ ) decreases at first and after x = 0.3, it begins to increase with further addition of the ferrite phase. The maximum dielectric constant ( $ε^{'}$ ) is 1092.08 at x = 0.9. The dielectric constant ( $ε^{'}$ ) and loss tangent (tanδ) display Maxwell-Wagner interfacial polarization and reduce from low to high frequency. All of the samples appear to be highly resistive indicating the reduction of leakage current. The dielectric constant ( $ε^{'}$ ) and resistivity show the opposite trend. P-E hysteresis loops indicate para-electric to ferroelectric transition.
Layered SrTiO<inf>3</inf>/BaTiO<inf>3</inf> composites with significantly enhanced dielectric permittivity and low loss
2023, Ceramics International
Ferroelectric ceramic materials are receiving increasing attention due to their extensive applications in electrical systems. In this work, three-layer BaTiO₃/SrTiO₃ ceramic composites consisting of one Ba_1-xTiO₃-Sr_xTiO₃ (at x = 5, 10, 20 and 30) composite interlayer sandwiched by two BaTiO₃ outer layers were fabricated. And the effects of SrTiO₃ modification on their phase structures, microstructures and dielectric performance were studied in detail. A pure perovskite phase was observed in the Ba_1-xTiO₃-Sr_xTiO₃ ceramic composites. The BaTiO₃ ceramic doping by SrTiO₃ exhibited refined grain size. With increased SrTiO₃ content, both the permittivity and dielectric loss have increased. Furthermore, a layered structure was designed to enhance the dielectric properties. Consequently, a high permittivity of 7118 and low loss of 0.028 were achieved at 10 kHz in BaTiO₃-30 w% SrTiO₃–BaTiO₃ three-layer ceramic composites. In summary, the introduction of SrTiO₃ is believed to reduce the BaTiO₃ Curie temperature and greatly improve its permittivity at room temperature. Furthermore, the accumulation of charge carriers at the interface significantly increases the permittivity, while preventing the transport of the charge carriers and reducing the loss. The ultrahigh permittivity and low loss make these composites promising candidates for microwave antennas, field effect transistors and dielectric capacitors.
Eu(III)–BaTiO<inf>3</inf> nanoparticles and BaTiO<inf>3</inf>/TiO<inf>2</inf>/Ti sheets; photocatalytic and electrocatalytic CO<inf>2</inf> reduction
2023, Materials Science in Semiconductor Processing
Perovskite barium titanate (BaTiO₃, BTO) has shown a high potential as catalysts. Eu(III) ion has been employed as a unique red-luminescence activator in a host metal oxide. Herein, Eu(III)-doped BTO nanoparticles (NPs) were synthesized, and their photocatalytic CO₂ reduction activities and products were examined. Major CO₂ reduction products were observed to be CH₃OH, CO, and CH₄. Doped Eu(III) ions were used as a tracer to discuss the roles of dopants by measuring photoluminescence (PL) properties and PL lifetimes. Electrocatalytic CO₂ reduction performances were evaluated using BTO electrodes directly grown on a TiO₂/Ti sheet, and Cu-deposited BTO electrodes. H₂ was a major product and formate was significantly increased upon Cu deposition on the surface. Surface oxidation states of BTO with dopant concentration and overlayer Cu metal were fully discussed by X-ray photoelectron spectroscopy. The surface electronic structure was altered by doping and metal deposition, and thereby the selectivity and productivity for CO₂ reduction were varied. The unique physicochemical properties and CO₂ reduction demonstration tests provide significant information on understanding CO₂ reduction mechanism and the development of BTO-based catalysts for energy and environment.

View all citing articles on Scopus

View full text

Characterization and Rietveld Refinement of A-site deficient Lanthanum doped Barium Titanate

Highlights

Abstract

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusions

J. Eur. Ceram. Soc.

J. Eur. Ceram. Soc.

J. Eur. Ceram. Soc.

Solid State Ionics

J. Rare Earths

Int. J. Inorg. Mater.

Mater. Lett.

Solid State Sci.

Solid State Ionics

J. Alloys Comp.

Physica B

Mater. Chem. Phys.

Curr. Appl. Phys.

J. Solid State Chem.

Mater. Chem. Phys.

Mater. Sci. Eng. B

Chem. Phys. Lett.

Physica B

Electroceramic: Materials Properties and Applications

Study of reoxidation in heavily La-doped barium titanate ceramics

J. Phys.: Conf. Ser.

Microstructural changes during the reduction/reoxidation process in donor doped BaTiO3 ceramics

J. Am. Ceram. Soc.

Theoretical study on interactions between oxygen vacancy and doped rare-earth elements in barium titanate

Jap. J. Appl. Phys.

Study of new relaxor materials in BaTiO3–BaZrO3–La2/3TiO3 system

Solid State Sci.

Colossal dielectric permittivity of BaTiO3-based nanocrystalline ceramics sintered by spark plasma sintering

J. Electroceram.

Electrical and structural properties of characteristics of lanthanum-doped barium titanate ceramics

J. Appl. Phys.

Infrared studies of perovskite titanates

Phys. Rev.

Infrared Spectra Inorganic Compounds

Investigation on FTIR spectra of barium calcium titanate ceramics

J. Electroceram.

Investigation on FTIR spectrum of barium titanate ceramics doped with alkali ions

Ferroelectrics

Microstructural changes during the reduction/reoxidation process in donor doped BaTiO₃ ceramics

Study of new relaxor materials in BaTiO₃–BaZrO₃–La_2/3TiO₃ system

Colossal dielectric permittivity of BaTiO₃-based nanocrystalline ceramics sintered by spark plasma sintering