• Janardan Singh

      Articles written in Bulletin of Materials Science

    • Dielectric and piezoelectric properties of neodymium oxide doped lead zirconate titanate ceramics

      Janardan Singh N C Soni S L Srivastava

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      The dielectric and electromechanical properties of lead zirconate titanate [Pb(Zr, Ti)O3] ceramic added with neodymium oxide have been systematically studied employing the vector impedance spectroscopic (VIS) technique. The specimens were prepared using the mixed oxide route by adding different mol% of Nd2O3 (0.1 to 7 mol%) in [Pb(Zr, Ti)O3] near morphotropic phase boundary. Piezoelectric equivalent circuit parameters 𝑅, 𝐿, $C_a$ in series and $C_b$ in parallel have been determined by simulating /Z/ and 𝛩 plots. Electromechanical coupling coefficients and strain constants for the radial modes show a peak at about 3 mol%, the dielectric constant peaks at about 1 mol% and voltage constants peak at about 0.75 mol% of Nd2O3.

    • Temperature dependence of electromechanical properties of PLZT 𝑥/57/43 ceramics

      A K Shukla V K Agrawal I M L Das Janardan Singh S L Srivastava

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      The compositions of lead lanthanum zirconate titanate PLZT [Pb(Zr0.57Ti0.43)O3 + 𝑥 at% of La, where 𝑥 = 3, 5, 6, 10 and 12] have been synthesized using mixed oxide route. The temperature dependent electromechanical parameters have been determined using vector impedance spectroscopy (VIS). The charge constant 𝑑31 and elastic compliance $s^{E}_{11}$ show a peak in all the samples at a temperature 𝑇mt much below the ferroelectric – paraelectric transition temperature, whereas the series resonance frequency 𝑓s shows a dip at these temperatures. The Poisson’s ratio 𝜎𝐸 increases with temperature 𝑇 showing a broad peak at a temperature higher than 𝑇mt. The voltage constant 𝑔31 decreases and the planar coupling coefficient 𝐾p remains constant up to half of the 𝑇mt and then falls sharply with 𝑇. Half of the 𝑇mt can, therefore, be used for specifying the working temperature limit of the piezoceramics for the device applications.

    • Dielectric response of PLZT ceramics 𝑥/57/43 across ferroelectric– paraelectric phase transition

      A K Shukla V K Agrawal I M L Das Janardan Singh S L Srivastava

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      The dielectric properties of lead lanthanum zirconate titanate (PLZT) ceramics [Pb(Zr0.57Ti0.43)O3 +𝑥 at% of La, 𝑥 = 3, 5, 6, 10 and 12] have been measured in the frequency range 1 Hz–1 MHz using the vector impedance spectroscopy (VIS) at different temperatures. All the compositions show both non-dispersive and dispersive dielectric responses in different temperature regions. The non-dispersive region obeys the universal dielectric response. A low frequency (< 1 kHz) relaxation phenomenon with a high value of distribution parameter `ℎ’ (∼0.4 to 0.6) has been observed in all the compositions around the temperature corresponding to themaximum dielectric constant (𝑇m). The activation energies as calculated from the relaxation and d.c. conduction processes are comparable. The ferroelectric phase transition is diffuse in nature and broadening of the peak increases with La content.

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