• R N P Choudhary

Articles written in Bulletin of Materials Science

• Synthesis and electrical studies of modified PbTiO3 ceramics: (Pb1−xCax) (Mn0·05W0·05Ti0·90) O3

Modified ceramics (Pb1−xCax)[(Mn0·5W0·5)0·10Ti0·90]O3 have been fabricated forx=0, 0·05, 0·10 and 0·15 by high temperature solid state reaction technique. XRD, SEM, DTA and electrical studies of the sample withx=0·10 have been performed. These studies show that the sample is homogeneous single phase perovskite type with tetragonal structure. The phase transition occurs at 330°C. Electrical behaviour of other samples have also been investigated as a function of frequency (1 kHz to 1 MHz) and temperature (26°C to 300°C). The samples withx=0·05 and 0·10 have low loss, low dielectric constant, and show negligible pyroelectric effect. The sample withx=0·15 has minimum values ofɛ and loss which are temperature independent up to about 200°C. It also shows good pyroelectric behaviour. Hence it may be of use in pyroelectric infrared sensors.

• Structural and dielectric properties of Pb(Li1/4Sm1/4Mo1/2)O3 ceramics

The ceramic samples of lithium-samarium modified lead molybdate, Pb(Li1/4 Sm1/4 Mo1/2)O3 (PLSM)—a member of ABO3 family were prepared by solid state reaction technique at ≈ 600–700°C. Preliminary X-ray analysis suggests the formation of single phase orthorhombic compound of PLSM. Studies of surface morphology, uniform particle/grain distribution, and presence of elements in the compound were completed using scanning electron microscope (SEM). Measurements of dielectric constant (ɛ), loss (tanδ) and conductivity (σ) at different frequencies and temperatures provided that the compound has a strong dielectric anomaly at 107°C.

• Studies of structural and electrical properties of Pb(Li1/4Eu1/4Mo1/2)O3 ceramics

Polycrystalline sample of Pb(Li1/4Eu1/4Mo1/2)O3 was prepared by usual ceramic route. X-ray diffraction, SEM and EDAX were used to check the formation, homogeneity and elements present in the compound. The measurement of dielectric constant (ɛ), dielectric loss (tanδ), hysteresis loop parameters (e.g. spontaneous polarization) as function of frequency and temperature suggest that the compound is a ferroelectric one and has a ferro-paraelectric phase transition at 112 ± 2°C. The measurement of dc resistivity both as function of biasing electric field and temperature of the compound suggests that the compound has negative temperature coefficient (NTC) of resistance above 100°C.

• Ferroelectric phase transition in Ba5RTi3Nb7O30 [R=Nd, Eu, Gd] ceramics

Polycrystalline samples of Ba5RTi3Nb7O30 [R=Nd, Eu, Gd], were prepared using high-temperature solid-state reaction technique. Preliminary X-ray structural analysis of the compounds shows the formation of single phase compounds (orthorhombic crystal system) at room temperature. Detailed studies of dielectric properties (ɛ, tanδ,σ) as a function of frequency (400 Hz to 10 kHz) and temperature (30° to 380°C) show that these compounds exhibit diffuse ferroelectric phase transition.

• Structural, impedance and electrical evaluation of complex perovskite: Ca(Mn$_{1/3}$Ni$_{1/3}$W$_{1/3}$)O$_3$

A complex perovskite Ca(Mn$_{1/3}$Ni$_{1/3}$W$_{1/3}$)O$_3$, abbreviated as CMNWO, is synthesized by adopting the solid-stateceramic procedure. The X-ray diffraction analysis of CMNWO shows that the present perovskite is acquiring a cubic crystal structure having the cell dimension of $a = 3.8321$ Å. The obtained cell parameter is in good agreement with the theoretical cell parameter obtained from the SPuDS-V2.19.05.14 code. The micrograph describes the uniform grain distribution in the CMNWO sample. The average crystallite size of the sample was found to be 50.98 nm, which was calculated using the Scherrer relation. The dielectric and electrical properties like dielectric constant, dissipation factor, impedance, electrical modulus and conductivity of CMNWO were studied. The activation energies were determined from the AC-conductivity data in the temperature range of 200–350$^{\circ}$C and 360–500$^{\circ}$C. The dielectric spectra with temperature suggest that the present CMNWO is semiconducting in nature and follows the negative temperature coefficient of resistance kind of behaviour.

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020