Temperature Solid State Reaction Technique Research Articles

Structure, ferroelectric and magnetic behavior in Mn doped 0.75 BiFeO3-0.25BaTiO3 ceramics

Lead-free polycrystalline 0.75 BiFe 1-xMn xO3-0.25BaTiO3 (x = 0.00, 0.01, 0.02 and 0.03 hereby designated as BF-BT) ceramics were synthesized by high temperature solid state reaction technique. This study dwells on the role of Mn doping on the structure, ferroelectric and magnetic behavior of BF-BT ceramics. Structural phase analysis of the samples carried out by X-ray diffraction and Raman scattering measurements revealed single phase distorted perovskite structure with rhombohedral symmetry. No alteration in crystal structure was observed with increasing Mn concentration. The average crystallite size of the compounds increases (12.9–27.8 nm) with increasing Mn concentration. The saturated value of ferroelectric polarization (Pr) was found to decrease with increasing Mn-concentration and a maximum remnant polarization (Pr) of 0.6 μC/cm2 was recorded at an applied field of 25 kV/cm for x = 0.00 sample. Leakage current density was found to increase with increase in Mn concentration. Oxidation states of the cations probed by X-ray photoelectron spectroscopy (XPS) suggested that Fe/Mn were in mixed state (+3/+2), while Ti-ion demonstrated (+3/+4) state. Presence of multivalence states of Fe/Mn/Ti causing distortion in the lattice (attributed to Jahn Teller) with increasing Mn concentration significantly affects the magnetic behavior of the ceramics. A maximum value of saturation magnetization of Ms∼0.80emu/gm was recorded for x = 0.03 composition.

Magnetic and Electric properties of the Multiferroic Composite (1-x)BiFeO3 - xBa5TbTi3V7O30

Using high temperature solid state reaction technique ceramic composites (1-x)BiFeO3 - xBa5TbTi3V7O30 having different x values are prepared. Basic crystal qualities are studied using XRD which shows that there’s a formation of BiFeO3 and Ba5TbTi3V7O30 phases. There observed change in the basic structure as x changes and is most distorted for x = 0.5. From SEM study, it is found that the grain size is minimum for pure ferroelectric sample and maximum for x = 0.5. Dielectric constant ( r) and Dielectric loss (tanδ) has been measured at wide temperature range (RT- 673 K). With increase in the value of x, there is also increase in Dielectric constant ( r) and is maximum for x = 1. Magnetic measurement is done at low temperature by VSM which shows that the magnetization is maximum for x = 0.3. HIGHLIGHTS One of the major limitations in the utility of multiferroic materials is that it has low dielectric value and low magnetization value A ferroelectric material is doped with the multiferroic materials and the electrical and magnetic properties are being analyzed There is an enhancement in the ferroelectric and ferromagnetic properties of the doped materials GRAPHICAL ABSTRACT

Influence of LTSSR and HTSSR synthesis methods on the structural properties of YFeO3 orthoferrite

The YFO ceramics have been synthesized using High Temperature Solid State Reaction (HTSSR) as well as Low Temperature Solid State Reaction (LTSSR) technique in powder form. The Perovskite orthorhombic YFeO3 phase has been identified in the x-ray studies of the powder samples prepared with HTSSR technique. In addition, 24 % of Y2O3 phase is also detected in the HTSSR powder samples. This phase reduced with increasing calcination time, however could not be suppressed below 8 % even after calcination for 72 h. Whereas, the powder samples prepared using LTSSR technique exhibit only pure YFeO3 phase, on calcination at 950 °C for 6hrs.Therefore found a more convenient and less time-consuming technique for the development of the orthorhombic YFeO3phase in YFO ceramics.

Influence of rare earth substitution on structure, photoluminescence emission properties and Judd-Ofelt analysis of ZnS:Eu3+ red phosphors

A series of Eu3+ doped ZnS red emitting phosphors were synthesized by conventional low temperature solid state reaction technique. The structural and spectroscopic characteristics of the prepared materials were examined by theoretical and experimental methods. The XRD results confirm the formation of hexagonal structured ZnS material. Similar morphology is obtained from TEM and SEM analysis and the particle size and grain size were calculated. The compositional analysis using EDS confirms the atomic percentage present in the materials. The optical band gap energy of the samples varied from 3.59 to 3.43 eV. The PL emission under excitation 390 nm has greater emission intensity at concentration x = 0.1 in Zn(1-x)S: xEu3+ material. The intense red emission (614 nm) for concentration x = 0.1 have CIE coordinates (0.6090, 0.3905) with color purity 90.41% and CCT 1629.26 K. The site symmetry of Eu3+ ions was explained using PL emission spectra. The intensity parameters Ω2, Ω4 and Ω6, radiative properties like branching ratio (βR), transition radiative parameter (AR), stimulated emission cross section σe, radiative life time (τR) was calculated from Judd-Ofelt theory. The luminescence decay kinetics was analyzed and the life time of material was calculated in millisecond (ms) range. The strong and intense red emission and the improved stimulated emission cross section offer Eu3+ doped ZnS material useful for designing optoelectronic device applications.

Synthesis, structural and microstructural properties of CBN ferroelectric ceramics

Ca x Ba1- x Nb2O6 (CBN) ceramics with tetragonal tungsten bronze (TTB) structures are very attractive from academic and technological fronts due to their stupendous ferroelectric properties. Polycrystalline samples of Ca x Ba1- x Nb2O5 were prepared by a high temperature solid state reaction technique. The phase formation, microstructure and optical properties of the prepared samples were investigated by X-ray diffraction, scanning electron microscope and Raman spectrometer, respectively. X-ray analysis confirms the partially filled tetragonal tungsten bronze (TTB) structure. Scanning electron micrographs provide information related to the morphology and grain size distribution of the samples. Detailed analysis of the structural and optical properties suggests that these samples have undergone a phase transition well above the room temperature.

Two steps enhancement of dual mode (UC and DS) behaviour of Ho3+/Yb3+ and Tm3+/Yb3+ co-doped GdVO4 phosphors: Improvement in spectral and color purity

In the present work, the dual mode (Upconversion and Downshifting) emission behavior of Tm3+/Yb3+ and Ho3+/Yb3+ co-doped GdVO4 phosphors synthesized via high temperature solid state reaction technique have been studied. The pure phase formation has been confirmed by X-rays diffraction (XRD) studies. The crystalline nature has been found to improve on calcining the phosphors at 1473 K and also by incorporation of TiO2. The surface particles’ shape and size have been studied by SEM technique. The vibrational behaviour of the vanadate host has been investigated by Fourier Transform Infrared (FTIR) measurements. The UV–vis absorption spectra show the formation of charge transfer band (CTB) in UV region due to (VO4)3 group. The non-linear upconversion (UC) spectra show intense blue and NIR emission in GdVO4: Tm3+/Yb3+ phosphor on excitation with 980 nm radiation, whereas intense green and red UC emissions are observed in GdVO4: Ho3+/Yb3+ phosphor. The downshifting (DS) behaviour has been investigated in both the phosphors which show the self activation behaviour of GdVO4 host along with some sharp peaks in blue and green regions due to f-f transitions in Tm3+ and Ho3+ ions. The dual mode (UC and DS) emission has been further improved on heating the samples at higher temperatures and also by incorporation of TiO2. The color of the phosphor samples in the UC emission spectra has been visualized by CIE diagram. The color purity enhances in both the phosphors by increasing the calcination temperature and also by addition of TiO2. The spectral purity has been also calculated for the UC emission spectra and its also shows the same trend. Such phosphors are applicable for the display devices in blue, green and red regions via dual mode processes.

Structural and electrical properties of Nd3+ doped ferroelectric barium sodium niobate ceramics

Ferroelectric polycrystalline samples of Ba4Na2Nb10O30 with rare earth neodymium ion, member of the family of TB, were prepared using a high temperature solid state reaction technique and studied their electrical properties in a range of temperature (RT-to 300 °C) at 1KHz. X-ray diffraction analysis of these compounds shows the formation of single phase tetragonal structure at room temperature. Detailed studies of the dielectric properties suggest that they have undergone diffuse ferroelectric–paraelectric phase transition well above the room temperature. It has also been found that as the concentration of the neodymium increases, Curie temperature observed to be decreased. Measurements of electrical DC Conductivity as a function of temperature suggest that the compounds have semi conductivity properties the temperature, with positive temperature coefficient of resistance (PTCR) behavior.

A novel bifunctional Dy3+ activated RbCaF3 single phase phosphor: Facile synthesis and dual-luminescence properties for WLEDs and dosimetry applications

A series of Dy3+ activated RbCaF3 phosphors was synthesized by the conventional high temperature solid state reaction technique under ambient atmosphere. The structural properties and morphology of synthesized compounds were analyzed by PXRD and FE-SEM, respectively. The chemical composition of synthesized phosphors was obtained by EDAX. The phosphor was excited at 386 nm and monitored at 484 and 574 nm, and the strongest peak was located at 484 nm (blue region). In addition, the point of RbCaF3:Dy3+ with calculated chromaticity coordinates in the CIE diagram was located in the yellow region. TL characteristics of the RbCaF3:Dy3+ phosphor was analyzed and the glow curve peak was emitted at 355 K. The symmetry factor, Balarin parameter, activation energy and frequency factor were calculated by Chen method from the TL glow curve, and the TL signal degradation was also analyzed.

Investigation of structural, dielectric and electrical properties of ZnFe2O4 composite

The polycrystalline sample of ZnFe2O4 was prepared by high temperature solid state reaction technique. The formation of the compound is confirmed by X-ray diffraction study at room temperature. The dielectric properties of the compound are studied in a wide temperature range as a function of the frequency. Analysis of frequency-dependent electrical data at different temperatures indicated a non-Debye-type temperature relaxation cycle in the compounds. DC and AC conductivity study show negative temperature coefficient of resistance (NTCR) behavior at different frequency. Frequency dependence AC conductivity obeyed Jonscher’s universal power law. The temperature dependence of the ac conductivity was fitted with Arrhenius equation and activation energies were calculated at different temperature ranges to know the conductive species involved in the conduction process.

Modulating the magnetic properties of BiFeO3 by addition of Ba5TbTi3V7O30

xBiFeO3-(1-x)Ba5TbTi3V7O30 (xBFO-BTTV) ceramic composites with different x values were prepared by high temperature solid state reaction technique and sintering at 1073K. The formation of composite structure consisting of BFO and BTTV phases was confirmed by XRD study. Surface morphology was studied by scanning electron microscope (SEM) and shows that structure with high density was obtained in the composite 0.3BFOBTTV whereas the average grain size increases by increasing x, i.e. by increasing amount of BiFeO3 in the system. Magnetic measurements were done in a wide temperature range, i.e. from 10 to 350K, by vibrating sample magnetometer (VSM) and showed that the magnetization changes by changing the value of x in the composite. BiFeO3 is antiferromagnetic in nature with weak ferromagnetism. Addition of Ba5TbTi3V7O30 enhances magnetic properties of the composite and maximal coercivity and remnant magnetization are obtained in the composite 0.7BFO-BTTV.

Investigation of Structural, Electrical and Thermal Characteristics of NdFeO3 Ceramic

The synthesis of single phase polycrystalline ceramic sample of NdFeO₃ by high temperature solid state reaction technique using high purity oxides has been reported. The structural parameters were investigated by Rietveld refinement program. The prepared ceramics show orthorhombic structure with space group Pnma. The frequency and temperature dependent dielectric constant, dielectric loss and ac conductivity of the compound have been studied. The dc conductivity has also been measured and its activation energies were calculated using Arrhenius relation. The calculated heat capacity (ΔCp) and enthalpy change (ΔH) of the compound are 0.068 J/gK and 2.3664 J/g respectively.<div><br></div>

Enhanced upconversion from Er3+/Yb3+ co-doped alkaline earth aluminates phosphor in presence Zn2+: A comparative study

Abstract In the present work, the upconversion emission spectra of Er3+/Yb3+co-doped CaAl2O4 (CAO), SrAl2O4 (SAO) and BaAl2O4 (BAO) phosphor samples have been studied in absence and presence of Zn2+. The samples were synthesized using high temperature solid state reaction technique at 1623 K. The X-ray diffraction (XRD) measurements have been carried out to verify the pure phase formation in all the three cases. Whereas the CAO and SAO samples show the monoclinic phase, the BAO sample shows hexagonal phase. The surface morphology of the three phosphor samples has been studied by scanning electron microscopy (SEM) technique. The Fourier-transform infrared (FTIR) and Raman measurements show the vibrational bands due to different groups present in the samples. The upconversion emission spectra of all the three samples show green and red emissions bands due to Er3+ ion on excitation with 980 nm laser. However, it is interesting to note that CAO phosphor emits very intense green and weak red emissions, the SAO and BAO phosphors give intense red and weak green emissions. However, the upconversion emission intensity (green as well as red both) in all the three samples is enhanced several times in presence of Zn2+ ions. The mechanism involved in UC emissions has been explained by partial energy level diagram.

Remarkable promotion of mechanical tensile strength of Mg1-xAxB2 superconductor via additions of ultra-high - ductile AZ61-alloy

Extruded Mg–(6%Al)–(1%Zn) ∼ (AZ61) alloy powder was applied as softener matter and grains sizes promoter in narrow range to replace on magnesium sites of Mg1-xAxB2 superconductor (where, x = 0.0,0.025,0.050,0.075 and 0.1 mol and A = AZ61) alloy) . Samples were synthesized via high temperature solid state reaction technique depending upon diffusion mechanism of Mg -vapor ions through added A-boron-matrix at 760 °C. Micro-structural features and grains sizes averages were estimated and monitored by both of 3D-AFM and SE-microscopy. Mechanical tensile was recording promising results with maximum tensile value of 52.3 MPa is for sample with x = 0.075 mol which is better than pure MgB2 (33.8 MPa.) by promotion ratio∼ 54.73%.

Synthesis, structure and luminescent properties of a new white phosphor Ba7(BO3)3(SiO4)Cl:Dy3+ for light-emitting diodes

A new Dy3+ activated Ba7(BO3)3(SiO4)Cl phosphor with complex anionic groups was synthesized by the high temperature solid state reaction technique. The X-ray powder diffraction analysis showed that the phosphors crystallized in polar space group P63mc of the hexagonal system. The excitation and emission spectra, decay curves and chromaticity coordinates were characterized to investigate the photoluminescence properties. The Ba7(BO3)3(SiO4)Cl:Dy3+ phosphors could be effectively excited by UV–visible light from 280 to 500 nm. The emission spectra exhibited three emission bands peaking at 480 (blue light), 576 (yellow light) and 665 nm (red light), which were due to the 4F9/2-6H15/2, 4F9/2-6H13/2 and 4F9/2-6H11/2 transitions of Dy3+, respectively. When Dy3+ concentration exceeded 12 mol%, the concentration quenching occurred. The critical distance between Dy3+ ions was calculated to be about 9.22 Å. In addition, the chromaticity coordinates of the phosphor are (0.33, 0.37), and the point is in the white region.

STUDY OF THE DIELECTRIC AND MICROSTRUCTURE PROPERTIES OF (1-x) CaCu3TI4O12 – (x) PbZr0.65Ti0.35O3 COMPOSITE

In this paper, structural, dielectric and electrical properties of calcium copper titanate and PbZr0.65Ti0.35O3 ceramic composite with composition (1-x) CaCu3Ti4O12 – (x) PbZr0.65Ti0.35O3 (where x = 0.00, 0.30, 0.50, 0.70 and 1.00) has been distinguished. The CaCu3Ti4O12 sample was prepared by employing a high temperature solid state reaction technique and PbZr0.65Ti0.35O3 synthesized by sol-gel route. X-ray diffraction (XRD), scanning electron micrograph (SEM), FT-IR spectrum (IR) was used to reach the structural properties of the studied compounds. The XRD and IR studies confirm the formation of pure phase for x = 0.00 and 1.00 concentrations i.e cubic and tetragonal, respectively. The SEM show change in the grain distribution, size and shape at addition of PbZr0.65Ti0.35O3. Dielectric measurements were made by using an impedance analyzer, the results show that the dielectric constant of the CCTO/PZT composite is greater than that of pure CCTO and than that of pure PZT. The temperature dependence of the ac conductivity indicated that the conduction process is due to singly and doubly ionized, and frequency dependence of the ac conductivity of composites follows Jonscher’s power law.

Dy3+-, Tb3+-, and Eu3+-activated NaCa4(BO3)3 phosphors for lighting based on near ultraviolet light emitting diodes

A variety of Dy3+-, Tb3+- and Eu3+-singly or doubly or triply activated NaCa4(BO3)3 phosphors for light emitting diodes applications were synthesized via a high temperature solid state reaction technique under an ambient atmosphere. These phosphors were studied by X-ray diffraction, scanning electron microscopy, photoluminescence excitation and emission spectra, Commission International de I'Eclairage chromaticity coordinates, and correlated color temperatures. The emission colors of Dy3+-, Tb3+-, and Eu3+-doped phosphors can be successfully tuned from green to yellow and then to white by appropriately changing the Tb3+ content and the excitation wavelengths. The correlated color temperatures can also be tailored from cold color to warm color. Furthermore, the energy transfer process from Dy3+ to Tb3+ in the Dy3+/Tb3+ codoped phosphors exists, which is discussed based on the luminescence spectra and energy level diagram analysis. The NaCa4(BO3)3:Dy3+, Tb3+, Eu3+ phosphors reported here demonstrate promising applications in the fields of near ultraviolet based light emitting diodes.

Luminescence properties of Eu3+ doped BaCa2MgSi2O8 phosphor and the influence of charge compensator in the host

The Eu3+ singly doped and Eu3+-R+ (R=Li, Na, K) codoped BaCa2MgSi2O8 phosphors were prepared through high temperature solid state reaction technique. The phase structures, morphologies and luminescence properties were investigated. The phosphors can be excited by 396nm radiation and exhibit red emission, the most intense emission locates at 614nm. The CIE (Commission Internationale de l’Eclairage, International Commission on Illumination) chromaticity coordinates (0.659, 0.341) are very close to the NTSC (National Television Standards Committee) standard values. The influence of R+ ions on the morphology, luminescence spectra, decay curves and thermal quenching properties were discussed, the emission intensity of Eu3+-Li+ codoped phosphor is higher than that of Eu3+-Na+ or Eu3+-K+, only Li+ can enhance the emission intensity in this study.

Effect of the concentration of the dopants (Er3 +, Yb3 + and Zn2 +) and temperature on the upconversion emission behavior of Er3 +/Yb3 + co-doped SrAl2O4 phosphor

Er3+/Yb3+ co-doped SrAl2O4 (SRA: Er3+, Yb3+) phosphor has been synthesized by high temperature solid state reaction technique. The pure phase formation has been confirmed by X-ray diffraction (XRD) measurements. The surface morphology is studied by scanning electron microscopy (SEM) technique. The FTIR measurements give the information of vibrational bands arising due to sample. The intense UC emission from SRA: Er3+, Yb3+ phosphor has been monitored on excitation with 980nm diode laser. The SRA: Er3+, Yb3+ samples prepared at 1473K show a dominant green emission. On the other hand it shows dominant red emission when the sample is heated to 1623K. Variation of concentration of Er3+ and Yb3+ ions in SRA: Er3+, Yb3+ phosphor suggests two possible mechanisms involved in UC emission process viz. cross relaxation (CR) process and energy back transfer (EBT) process, respectively. The cross relaxation mechanism seems to play a major role. The UC emission efficiency is enhanced several times on co-doping of Zn2+ ion replacing Al3+ or Sr2+ in SRA: Er3+, Yb3+ phosphor sample. The color of the UC emission can be tuned from green to red region by varying the concentration of zinc.

Structure and luminescence properties of Sm3+ doped Y2MoO6 phosphor under near ultraviolet light excitation

A series of Sm3+ doped Y2MoO6 were prepared through high temperature solid state reaction technique. Their phase structures, morphologies and luminescence properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectrometry. The most intense absorption of Y2MoO6 host occurred at 367 nm. Energy transfer from host lattice to Sm3+ ions could be observed, and the schematic diagram of energy transfer was constructed. The critical energy transfer distance and energy transfer mechanism between Sm3+ ions were discussed in detail. Considering the high color purity and appropriate emission intensity, Sm3+ doped Y2MoO6 could be a promising phosphor under near ultraviolet light excitation.

Tunable Emission Phosphor Ca0.75Sr0.2Mg1.05(Si2O6):Eu2+, Mn2+: Luminescence and Mechanism of Host, Energy Transfer of Eu2+ → Mn2+, Eu2+ → Host, and Host → Mn2+

A series of Ca0.75Sr0.2Mg1.05(Si2O6) (CSMS):xEu2+, yMn2+ phosphors were synthesized by a high temperature solid state reaction technique in a reducing atmosphere (1250 °C, 4 h). Under excitation of 270 nm, the emission spectrum of CSMS host is characterized by a broad band with two distinct emission peaks (453 and 580 nm), tailing on the energy side from approximately 350 to 800 nm. Thus, there is an orange-yellow emission in CSMS host. The different trap depths of thermoluminescence spectra (E1 = 0.6453 eV, E2 = 0.8271 eV) are measured and these traps will fade away when Eu2+ or Mn2+ ions are doped. In addition, the blue-shift, red-shift, and intensity changes of temperature dependence emission spectra in Ca0.75Sr0.2Mg1.05(Si2O6) host are observed with higher temperature. For Eu2+ single doped CSMS, which has an obvious absorption in the near-ultraviolet and blue region with a wide band of excitation spectrum ranging from 200 to 450 nm monitored at 453 nm. And the emission spectrum presents an obvious re...