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Ceramic compositions of (Ba1-xCdx)(Zr0.13Ti0.87)O3 with x = 0, 0.02, 0.04 and 0.06 exhibit a layered microstructure and enhanced grain growth (~ 50 µm for x = 0.06). The XRD and Raman measurements reveal the coexistence of rhombohedral, orthorhombic and tetragonal phase, and with increase in Cd content the rhombohedral phase fraction increases significantly (10–56%) whereas the phase fraction of tetragonal decreases (62–14%). Pyroelectric coefficient (p) increases with Cd content and a large value of p ~ 1841 μCm−2 K−1 is obtained for x = 0.06. Current responsivity Fi is maximum (~ 849 pmV-1) for x = 0.02, whereas the voltage responsivity Fv (~45 ×10−3 m2 C−1), detectivity Fd (~48 μPa−1/2) and thermal energy harvesting figure of merit Fe* (~34 pJ−1 m3) are maximum for x = 0.06. Ease of polarization rotation in the polymorphic state due to the coexistence of rhombohedral, orthorhombic and tetragonal phases, and a large ceramic grain size contribute to the strong pyroelectric response.

Cadmium doped barium zirconate titanate (Ba 1−x Cd x )(Zr 0.13 Ti 0.87 )O 3 (BCDZT) ferroelectric ceramic compositions with x =0, 0.02, 0.04 and 0.06 have been prepared by solid state reaction method. X-ray diffraction studies reveal a pseudocubic structure. For increasing Cd content, the bulk ceramic micro-structure reveals an increasing grain size and density. Variations in the dielectric, piezoelectric and unipolar electric field induced strain characteristics are discussed. Increasing Cd content reduces the coercive field, increases the remnant polarization and does not affect the ferroelectric-paraelectric phase transition temperature (~60 °C). An optimum Cd content x =0.06 produces highly resistive ceramics with low dielectric loss (tan δ =0.019), and a maximum value of piezoelectric charge constant d 33 =114 pC/N and unipolar electro-strain of ~0.07%.

Nickel ferrite (NiFe 2 O 4 ) powders derived by auto-combustion synthesis using three different fuels (citric acid, glycine and dl -alanine) have been characterized. The sintering behavior of ceramics using these powders has been compared. Oxygen balance (OB) setting for the chemical reaction is found to regulate the combustion reaction rate. A rapid reaction rate and a high flame temperature are achieved with d l alanine fuel yielding single phase NiFe 2 O 4 powder in the as-burnt stage, whereas powders derived with citric acid and glycine fuels show poor crystallinity and necessitate post-annealing. The powder particles are largely agglomerated with a non-uniform distribution in shape and size, and the average particle size is estimated in the range ~ 54–71 nm. Powders derived from dl -alanine fuel show better phase purity, smaller crystallite size, larger surface area and superior sintering behavior. Additional Raman modes discerned for dl -alanine derived powder support a 1:1 ordering of Ni 2+ and Fe 3+ at the octahedral sites relating to microscopic tetragonal P 4 1 22 symmetry expected theoretically for the formation of NiFe 2 O 4 with inverse spinel structure. Microstructure of sintered ceramics depends on the precursor powders that are used and sintering at 1200 °C is found to be optimum. Citric acid and glycine derived powders yield high saturation magnetization ( M s ~47–49 emu/g), but poor dielectric properties, whereas dl -alanine derived powders yield ceramics with high resistivity (~3.4×10 8 Ω cm), low dielectric loss (tan δ ~0.003 at 1 MHz) and high magnetization (46 emu/g). Dielectric dispersion and impedance analysis show good correlation with the changes in the ceramic microstructure.

Dielectric and magnetic properties of NiFe2O4 ceramics prepared with powders using DL-alanine fuel in the sol–gel auto combustion technique are studied. DL-alanine fuel yields crystalline as-burnt powders, and when used for ceramic processing yields varying microstructure at different sintering temperatures. The dielectric properties are influenced by the resulting microstructure and the magnetic properties show slight change in saturation magnetization Ms (~44 – 46 emu/g). The coercive fields, dielectric losses and dispersion are reduced considerably at higher sintering temperatures (1200–1300 °C). The influence of changing microstructure is analyzed through dielectric response, complex impedance analysis and electrical modulus spectroscopy in the frequency range (10−2–107 Hz) to understand the interactions from the grain and grain boundary phases. Sintering at 1200 °C, is found to be optimum, yields lower losses & reduced dielectric dispersion, and high resistivity (3.4×108 Ω cm).