Showing papers by "Ajit R. Kulkarni published in 2016"
TL;DR: In this paper, a new lead-free (100−x)Li0.12Na0.88NbO3-xBaTiO3 (0 ≤ x ≤ 40) piezoelectric ceramics have been synthesized using conventional Ceramics processing route and a partial phase diagram has been established based on temperature-dependent permittivity data for this new system and a almost vertical temperature-independent MPB is observed.
Abstract: New lead-free (100−x)Li0.12Na0.88NbO3-xBaTiO3 (0 ≤ x ≤ 40) piezoelectric ceramics have been synthesized using conventional ceramics processing route. Structural analysis revealed an existence of morphotropic phase boundary (MPB), separating orthorhombic and tetragonal phases, between the BaTiO3 content, x = 10–12.5. A partial phase diagram has been established based on temperature-dependent permittivity data for this new system and a almost vertical temperature-independent MPB is observed. Improvement in electrical properties near MPB (e.g., for x = 12.5; er = 8842 at Tm and 795 at room temperature, d33 = 30 pC/N, kp = 12.0%, Qm = 162, Pr = 11.2 μC/cm2, Ec = 19.2 kV/cm, d33∗ = 174 pm/V) is observed, and is attributed to the ease of polarization rotation due to coexistence of orthorhombic and tetragonal phases. The results show that these materials could be suitable for piezoelectric vibrators and ultrasonic transducer applications. The sample with x = 25, also exhibited high dielectric permittivity, er = 2400, and low dielectric loss, tanδ = 0.033 at room temperature which could be suitable for capacitor (X7R/Z5U) applications.
21 citations
TL;DR: Particulate magnetoelectric composites of 1−x(0.5PNN)-0.35PT-0.15PZ)+xCFO with x ǫ = 0.3 have shown highest voltage coefficient (αE) of 13.2 mV/cm Oe as discussed by the authors.
20 citations
TL;DR: The magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films prepared on a glass substrate using RF magnetron sputtering has been investigated in this paper.
Abstract: The magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films prepared on a glass substrate using RF magnetron sputtering has been investigated in this work. PMN-PT thin films (i.e. PMN-PT/LCMO/Pt/Ti/glass) deposited on glass were used as a substrate for deposition of ZnFe2O4 thin films. ZnFe2O4 thin films were annealed ex situ at different temperatures. Structural, magnetic, ferroelectric, dielectric and magneto-dielectric studies were carried out on these multiferroic bilayer thin films. Structural studies revealed the presence of each layer in its respective single phase. Magnetic and ferroelectric studies revealed the ferromagnetic and ferroelectric behaviors of these bilayers. To quantify the magnetoelectric coupling, the dielectric constant of the bilayer was measured at room temperature as a function of frequency with and without the applied magnetic field. The magneto-dielectric response MD(%) was calculated by finding the relative change in dielectric constant at 1 kHz as a percentage. The observed MD response was correlated with magnetization of the ferrite layer. An MD response of 2.60% was found for a bilayer film annealed at 350 °C. At this particular annealing temperature, the ZnFe2O4 layer also has the highest saturation magnetization of 1900 G.
12 citations
TL;DR: In this paper, the conductivity of glass-ceramics was derived using impedance spectroscopy data for all soak times and correlated to the crystalline volume content, which was attributed to formation of 3D conducting channel network.
Abstract: Glass–ceramics derived from Li 2 O–Al 2 O 3 –TiO 2 –P 2 O 5 vitreous system were obtained by isothermal heat treatment at 700 °C, for different soak times ranging from 0 to 60 h. Phase analysis revealed mixture of amorphous and crystalline phases for short soak times ( 1 + x Al x Ti 2 − x (PO 4 ) 3 (LATP) along with secondary AlPO 4 and TiO 2 , previously reported. Microstructural evolution with soak time was imaged using high resolution scanning electron microscope (SEM). Crystalline volume fraction in glass–ceramics was estimated from image analysis and it followed Kolmogorov–Johnson–Mehl–Avrami (KJMA) equation. Conductivity of glass–ceramics was derived using impedance spectroscopy data for all soak times and correlated to the crystalline volume content. After attaining a critical volume of crystalline phase/s, conductivity increased significantly and was observed to follow the scaling equation σ dc ~ (V − V c ) β , where σ dc is dc conductivity, V is crystalline volume content, V c is threshold value of crystalline volume content above which sudden increase in conductivity was observed and β is scaling exponent. V c ≈ 30% was in accordance with percolation scaling law and is attributed to formation of 3D conducting channel network in the glass–ceramics microstructure.
11 citations
TL;DR: In this article, mesoporous strontium hydroxyapatite (SrHAp) nanorod formation was successfully achieved even at temperatures as low as 140 °C with 1 min hold time.
Abstract: Synthesis of mesoporous strontium hydroxyapatite (SrHAp) nanorods was carried out in a microwave without using any capping agent or surfactant. Nanorod formation was successfully achieved even at temperatures as low as 140 °C with 1 min hold time. Field emission gun transmission electron microscopy (FEG-TEM) and scanning electron microscopy (SEM) indicated monodisperse, uniform and mesoporous nanorods with average dimensions: length 98.87 nm, width 18.87 nm and pore size 2–5 nm. XRD analysis showed that the sample consisted of a single phase made up of highly crystalline nanorods with a P63/m symmetry group. Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDX) confirmed that the chemical and elemental composition was that of strontium hydroxyapatite. Surface area and pore volume were calculated from nitrogen adsorption and desorption isotherms as 40.13 m2 g−1 and 0.45 cm3 g−1, respectively. The material was found to be non toxic to NIH3T3, MCF-7 and Zr-75 cells even at concentrations of 0.25 mg ml−1, and after 24 and 48 hours of incubation. Thus, owing to its high surface area, pore volume and good cell viability, this material showed good potential for anticancer and other drug delivery applications.
11 citations
TL;DR: In this paper, the colossal dielectric behavior of T-type La2CuO4-δ (LCO) ceramics synthesized in fine grained form using wet chemical "Pechini" process, followed by annealing in argon (Ar) atmosphere was presented.
8 citations
TL;DR: In this article, temperature dependent X-ray diffraction and dielectric properties of perovskite (Ba0.76Ca0.24)(Zr0.04Ti0.96)O3 ceramic were investigated.
Abstract: In this work the temperature dependent X-ray diffraction and dielectric properties of perovskite (Ba0.76Ca0.24)(Zr0.04Ti0.96)O3 ceramic were investigated. X-ray diffraction studies indicated the unit cell structure to be tetragonal (space group: P4/mmm) upto 800°C and thereafter it becomes orthorhombic (space group: Pmmm). The chemical composition was determined using energy dispersive X-ray. Dielectric studies exhibited two dielectric relaxations at 20°C and a high temperature phase transition at 855°C with the permittivity value of 1.65×105 at 1 kHz which places the present ceramic system in the list of potential candidate for intended high temperature applications. The result shows that capacitor has a resonance frequency higher than 0.44 MHz at 820°C which shifts towards 3.4 kHz at 1100°C depending on the value of its capacitance. The measured value of d33 was found to be 197 pC/N. The field dependent polarization and strain studies at room temperature indicated that (Ba0.76Ca0.24)(Zr0.04Ti0.9...
8 citations
TL;DR: In this article, the microstructures of the samples sintered at different temperatures and durations to optimize the sintering conditions were analyzed by analyzing the microstructure and electrical properties of Li0.12Na0.88NbO3 ceramics.
Abstract: Sintering behavior in Li0.12Na0.88NbO3 (LNN-12) ceramics has been investigated by analyzing the microstructures of the samples sintered at different temperatures (1050–1250 °C) and durations (1–6 h) to optimize the sintering conditions. An excess amount of Li2CO3 was added (1, 3, 5 mol%) to stoichiometric LNN-12 in order to compensate for the probable alkaline element loss at higher optimized sintering temperature. The addition of excess Li2CO3 into the starting materials and the effect of it on microstructure and electrical properties were investigated. Microstructural study of Li2CO3-added samples revealed abnormal grain growth, a characteristic feature of liquid phase sintering due to the low melting Li2CO3. The temperature and frequency dependence of dielectric constant shows two phase transitions in temperature dependence and low-frequency dispersion in the frequency dependence of dielectric plot. The observed frequency dispersion is attributed to dominant DC conductivity. The conduction mechanism was identified as diffusion of intrinsic Li+ ion. The room-temperature dielectric constant and loss factor were found to increase with increase in Li2CO3 addition from 160 to 690 and 0.02 to 0.04, respectively. The electrical conductivity was found to increase two orders of magnitude (10−12–10−10 Ω−1 cm−1) in Li2CO3-added samples as compared to stoichiometric composition. The results obtained here give a strong evidence of the stoichiometry–microstructure and electrical properties correlation, thus emphasizing on the importance of processing parameters to tune the desired properties in Li0.12Na0.88NbO3 ceramics.
2 citations
10 May 2016
TL;DR: In this paper, the crystal symmetry, space group and unit cell dimensions were determined from the XRD data of Ba(Fe1/2Nb 1/2)O3 using FullProf software, whereas crystallite size and lattice strain were estimated using Williamson-Hall approach.
Abstract: (1-x)PVDF-xBa(Fe1/2Nb1/2)O3 ceramic-polymer composites with x = 0.025, 0.05, 0.10, 0.15 were prepared using melt-mixing technique. The crystal symmetry, space group and unit cell dimensions were determined from the XRD data of Ba(Fe1/2Nb1/2)O3 using FullProf software, whereas crystallite size and lattice strain were estimated using Williamson-Hall approach. The distribution of Ba(Fe1/2Nb1/2)O3 particles in the PVDF matrix were examined on the cryo-fractured surfaces using a scanning electron microscope. Cole-Cole and pseudo Cole-Cole analysis suggested the dielectric relaxation in this system to be of non-Debye type. Filler concentration dependent real and imaginary parts of dielectric constant as well as ac conductivity data followed definite trends of exponential growth types of variation.
1 citations
10 May 2016
TL;DR: In this paper, a lead-free perovskite Ba(Ga 1/2Nb1/2)0.25Ti0.75O3 was prepared using conventional ceramic technique at 1450°C/5h in air atmosphere and characterized by X-ray diffraction, scanning electron microscopy, dielectric and impedance studies.
Abstract: Lead-free perovskite Ba(Ga1/2Nb1/2)0.25Ti0.75O3 was prepared using conventional ceramic technique at 1450°C/5h in air atmosphere and characterized by X-ray diffraction, scanning electron microscopy, dielectric and impedance studies. The crystal symmetry, space group and unit cell dimensions were derived from the experimental results using FullProf software. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space groupPm3m(221). EDX and SEM studies were carried to study the quality and purity of the compound. Partial replacement of Ti4+ with pseudo-cation((Ga1/23+Nb1/25+)4+) significantly reduces the dielectric constant as well as loss tangent values and improves the frequency and temperature stability of the dielectric properties and exhibited a low value of temperature coefficient of capacitance (<±7%) in the working temperature range (up to +125°C), which meets the specifications for ‘Z5R’ of Class I dielectrics of Electronic Industries Association. Hence, t...