Papers by Keyword: Impedance Spectroscopy

Abstract: Aiming at the shortcomings of large volume, high cost and long detection cycle of traditional solid propellant aging detection methods, a solid propellant aging detection method based on impedance spectroscopy is proposed. Firstly, the internal impedance of the solid propellant changes after aging, and a portable solid propellant impedance spectrum acquisition system based on impedance spectroscopy is designed based on the principle of electrochemical impedance spectroscopy, and the real and imaginary parts of the impedance spectrum are obtained. Secondly, in order to reduce the data dimension of the classification algorithm, the KPCA (Nuclear Principal Component Analysis) feature extraction algorithm is used to extract the impedance spectrum features of the solid propellant. Then, according to the impedance spectrum characteristics, the BP neural network is used for classification training, and the correspondence between the impedance spectrum and the aging time is obtained. Finally, the feasibility and effectiveness of the proposed method are verified on the physical platform, and the results show that the proposed method has the advantages of high precision and accurate classification, and can effectively predict the aging degree of solid propellant.

Abstract: The conventional solid-state reaction method was used to prepare the lead-free solid-solution (1-x)Ba_0.06(Na_0.5Bi_0.5)_0.94TiO₃-xNaTaO₃; 0 ≤ x ≤ 1. X-ray diffraction analysis of all the compositions of the series confirmed the solid solution’s successful formation. The electrical impedance and conductivity of the material were studied using the impedance spectroscopy method at temperatures ranging from room temperature to 500^○C. For the Ba_0.06(Na_0.5Bi_0.5)_0.94TiO₃ rich compositions ac conductivity increased with frequency at all temperatures, whereas for the NaTaO₃ rich compositions ac conductivity exhibited a frequency-independent behaviour. As the amount of NaTaO₃ incorporated into the compound Ba_0.06(Na_0.5Bi_0.5)_0.94TiO₃ was increased, a transition occurred in the electrical impedance, specifically, the impedance values shifted from low to high. A theoretical model based on correlated barrier hopping (CBH) has been used to explain the conduction mechanism in these solid solutions.

Abstract: Iron substituted Lead zirconate titanate nanoparticles Pb (Zr_0.52Ti_0.48) _1-x Fe_xO_3-x (PZTFx) (for (x=0.00, 0.025, 0.05, 0.075, 0.10, 0.15 and 0.20) was prepared using the sol-gel route in the morphotropic phase boundary (MPB) region. The X-ray diffraction data revealed the formation of both rhombohedral and tetragonal structures. The microstructural properties of the compounds were examined through the scanning electron microscopy (SEM) technique. The impedance spectroscopy and conductivity spectroscopy were carried out over a wide range of temperatures (RT–400°C) and frequencies (100 Hz–2 MHz) to investigate the grain and grain boundary effect on the electrical properties of PZTFx. The complex impedance analysis data have been presented in the Nyquist plot which is used to identify the corresponding equivalent circuit and fundamental circuit parameters. Cole– Cole plots indicate Debye-type dielectric relaxation and the grain boundaries resistance is dominant at room temperature. The Nyquist plot showed the negative temperature coefficient of resistance (NTCR) character of PZTFx ceramics. The dielectric properties of (PZTFx) ceramics as a function of temperature are studied and displayed a resonance phenomenon for all samples. Temperature-dependent conductivity behavior indicated an Arrhenius type of thermally activated process in the low-temperature region. Activation energy has been calculated from the temperature-dependent DC electrical conductivity measurements for all the samples.

Abstract: High purity of Li₇La₃Zr_2-xSn_xO₁₂ (x = 0.00, 0.50, 1.00, 1.50 and 1.00) samples that formed garnet-type crystal structure were prepared using biopolymer sol-gel method. The structure phase of Li₇La₃Zr_2-xSn_xO₁₂ (x = 0.00, 0.50, 1.00, 1.50 and 1.00) powder was indexed with the parent composition of Li₇La₃Zr₂O₁₂ structure with space group of Ia-3d for cubic phase. Impedance spectroscopy analysis was used to determine the conductivity of Li₇La₃Zr_2-xSn_xO₁₂ (x = 0.00, 0.50, 1.00, 1.50 and 1.00) samples. The samples exhibit the conductivity about 10^-6 to 10^-4 Scm^-1 .The SEM micrographs reveal that the grain of the samples exhibits well developed particles of irregular shape.

Abstract: High purity Li₇La₃Zr_1.0Sn_1.0O₁₂ samples that formed garnet-type crystal structure were prepared using biopolymer sol-gel method. The structure phase analysis of Li₇La₃Zr_1.0Sn_1.0O₁₂ powder was determined by using X-ray Diffraction (XRD). Impedance spectroscopy analysis was used to determine the electrical properties of Li₇La₃Zr_1.0Sn_1.0O_12. The electrical properties of the sample was observed from conductivity and resistance plots. The heterogeneity of sample was observed from Z’ and M” spectroscopic plot.

Abstract: The 5 mol% Fe-doped BaTiO₃ ceramic has been synthesized by using solid-state method. The sample was characterized by X-ray diffraction (XRD) and Impedance spectroscopy. It is interesting to note that the sample can developed a phase transformation between 1000 °C to 1350 °C. The XRD results showed that sample exhibited cubic structure when heated at 1000 °C and developed oxygen non-stoichiometry when it was heated at 1350 °C for 8 hours. It was confirmed by the ceramic color changes. The dielectric properties of the sample is relatively low which is due to the oxygen non-stoichiometry effect and gives the dielectric constant, ε_r value around 150 at 30 °C with frequency 1 kHz. The capacitance value of this sample lies within 10^-8 to 10^-10 which represents that the electrical properties of the sample has shown bulk and grain boundary response. There are pores that can be observed from the SEM images indicates the porosity of the sample which is in a good agreement with the low dielectric constant value. Moreover, the grains are composed of rectangular orientations, hexagonal shapes and inhomogeneous microstructures that might represent the coexistence of tetragonal and hexagonal phase of the sample.

Abstract: The BaTi_0.88Zr_0.12O₃ ceramic has been synthesized by using a conventional solid-state reaction method and sintered at 1450 °C in air for 3 hours. The structural and dielectric properties of the sample were investigated. It was found that the sample exhibited tetragonal structure with space group P4mm. The maximum dielectric constant, ε_r value was obtained at T_c (70 °C) about 2800 measured at 1 kHz. The dielectric peak was broad which might be due to the pinching effect. However, maximum ε_r value was quite low may be attributed by the T_c and other phase transition point might be not fully coalescence. Another phase transition temperature was vaguely observed around 30 °C to 40 °C. The dielectric properties of the sample were dominated by the grain effect with capacitance values lie within range of 10^-10 to 10^-9. The SEM images shows that the average grain size of the sample was quite small about 2.9087 μm. It might be due to the contribution of Zr⁴⁺ with lower grain growth rate.

Abstract: A single-phase of Li₇La₃Ce₂O₁₂ samples that formed garnet-type crystal structure were prepared using the conventional solid-state method. Li₇La₃Ce₂O₁₂ formed a tetragonal garnet-type structure with the space group of I4/mmm. Impedance spectroscopy data show that Li₇La₃Ce₂O₁₂ can be classified as the ionic conductor as it has a mixture of ionic and electronic conductivities. Their electrical conductivities also obey Jonscher universal power law.

Abstract: The dielectric properties and crystal structure of Ba_0.85Sr_0.15TiO₃ and Ba_0.85Sr_0.15Ti_0.92Zr_0.08O₃ ceramics were studied. The samples were synthesized by using solid-state method. The results show that the samples were single phase. The Ba_0.85Sr_0.15TiO₃ exhibited tetragonal structure (space group P4mm), while with addition of 8 mol% Zr into Ba_0.85Sr_0.15TiO₃ it shows that the sample exhibited orthorhombic structure (space group Amm2). The dielectric constant value increased from 1094 for pure, up to 4211 for Ba_0.85Sr_0.15Ti_0.92Zr_0.08O₃ ceramic at T_c measured at 1 kHz. The T_c decreased from 80 °C down to 60 °C as 8 mol% Zr ions doped into Ba_0.85Sr_0.15TiO₃ composition. The Ba_0.85Sr_0.15Ti_0.92Zr_0.08O₃ ceramic exhibited lower dielectric loss, tan δ about 0.006 compared to Ba_0.85Sr_0.15TiO₃ ceramic (tan δ = 0.009) when measured at 110 °C with frequency 1 kHz. The slope at low frequency region in capacitance vs frequency plot for both samples attributed by the grain boundary effect, whereas the high frequency plateau associated with the bulk response. The impedance spectroscopy analysis results show that both samples are dominated by the bulk response when an incomplete semicircle arc was observed in Zʺ vs Zʹ plot.

Abstract: The BaTi_0.905Sn_0.095O₃ ceramic has been synthesized by using a solid-state method and sintered at 1450 °C in air for 3 hours. The doping effect of 9.5 mol% Sn into BaTiO₃ ceramic towards its crystal structure, dielectric properties and microstructure were investigated. The X-ray diffraction (XRD) analysis shows that the sample exhibited tetragonal structure with space group p4mm. The dielectric constant, ε_r measurement revealed that the sample reached the maximum ε_r value about 4393 when measured at T_c around 45 °C with frequency 1 kHz. The dielectric loss value was considerably low about below than 0.3 for the temperature range from 30 °C to 150 °C measured at 1 kHz. The capacitance value range lies between 10^-9 and 10^-10 indicates the bulk effect has dominated the electrical properties of the sample. It shows a good correlation with the microstructure results where the grains were well developed and homogenously distributed.