Comparative study of dielectric properties of MgNb<SUB>2</SUB>O<SUB>6</SUB> prepared by molten salt and ceramic method

Magnesium niobate (MgNb<SUB>2</SUB>O<SUB>6</SUB>) powder was synthesized by the conventional ceramic route as well as by the molten salt route using a eutectic mixture of NaCl-KCl as the salt and Mg(NO<SUB>3</SUB>)<SUB>2</SUB>&#183;6H<SUB>2</SUB>O and TiO<SUB>2</SUB> as the starting materials. Pure phase of MgNb<SUB>2</SUB>O<SUB>6</SUB> could be obtained by the molten salt method at 1100&#176;C. However, in ceramic method the pure phase of MgNb<SUB>2</SUB>O<SUB>6</SUB> was obtained by heating at 1025&#176;C for 20 h. On sintering at 1100&#176;C the dielectric constant and dielectric loss of MgNb<SUB>2</SUB>O<SUB>6</SUB> obtained by the molten salt method was found to be 19.5 and 0.004 at 100 kHz at room temperature. Lower values were obtained for these oxides prepared by the ceramic route, 16.6 and 0.000518, respectively. In both cases the dielectric constant was quite stable with frequency

Investigation of Ba<SUB>2&#8722;x</SUB>Sr<SUB>x</SUB>TiO<SUB>4</SUB>: structural aspects and dielectric properties

Investigation of solid solution of barium-strontium orthotitanates of the type, Ba<SUB>2&#8722;x</SUB> Sr <SUB>x</SUB> TiO<SUB>4</SUB> (0 &#8804;x&#8804; 2), show that pure phases exist only for the end members, Ba<SUB>2</SUB>TiO<SUB>4</SUB> and Sr<SUB>2</SUB>TiO<SUB>4</SUB>, crystallizing in the &#946;-K<SUB>2</SUB>SO<SUB>4</SUB> and K<SUB>2</SUB>NiF<SUB>4</SUB> structures, respectively. The intermediate compositions (till&#8805; 1) lead to a biphasic mixture of two Ba<SUB>2</SUB>TiO<SUB>4</SUB>-type phases (probably through a spinodal decomposition) with decreasing lattice parameters, indicating Sr-substitution in both the phases. For x &#62; 1, Sr<SUB>2</SUB>TiO<SUB>4</SUB> along with a secondary phase is obtained. The dielectric constant and dielectric loss were found to decrease with Sr substitution till the nominal composition of x = 1. However, pure Sr<SUB>2</SUB>TiO<SUB>4</SUB> shows higher dielectric constant compared to the solid solution composition. Sr<SUB>2</SUB>TiO<SUB>4</SUB> shows very high temperature stability of the dielectric constant

Sintered compacts of nano and micron-sized BaTiO<SUB>3</SUB>: dramatic influence on the microstructure and dielectric properties

Sintered compacts of nano-sized and micron-sized BaTiO<SUB>3</SUB> show sharp ferroelectric transition and high dielectric constant at specific compositions. The sintered compacts with 1 wt% nano-BaTiO<SUB>3</SUB> show a maximum dielectric constant of 1680. At the transition temperature (T<SUB>c</SUB>) there are two maxima at 0.5 and 2 wt%. The variation in the dielectric constant at T<SUB>c</SUB> is also reflected in the behavior of the ferroelectric transition as studied by differential scanning calorimetry. This interesting oscillatory variation of the dielectric constant and dielectric loss with increase in the amount of nanoparticles in the sintered compacts is observed for the first time. The variation of the dielectric properties and the ferroelectric transition of the sintered compacts could be related to subtle changes in the microstructure

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Not AvailableCoccinellid species belonging to fifteen genera, under five tribes of the family Coccinellidae were collected and identified in this study. Harmonia (Fab.) was the most predominant in southern regions and Coccinella septumpunctata L. was more abundant in the northern and hill regions. Margalef richness index ranged from 9.07 to 14.00 while the species richness directly measured by Hills number H0 ranged from 5-10, with highest species richness present at Malan, Himachal Pradesh. The highest predation was observed in female H. octomaculata which fed on a maximum of 8.00, 7.42 and 6.59 brown planthopper (BPH), WBPH white backed planthopper (WBPH) and green leafhopper (GLH) respectively per day, while the lowest was observed in Propylea dissecta which fed on 3.18 to 4.50 hoppers per day. Coccinellids like H. octomaculata can be utilized in biological control programmes as a part of Integrated Pest Management to reduce pest outbreakNot Availabl

Superior energy storage performance and fatigue resistance in ferroelectric BCZT thin films grown in an oxygen-rich atmosphere

Ferroelectric properties of chemical-solution-deposited Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCZT) thin films in the 200 nm thickness range, grown in air and oxygen-rich atmospheres, were investigated. Oxygen-processed BCZT thin films were found to have very slim hysteresis with higher polarization, lower remanent polarization (P-r), much lower coercivity and much higher dielectric breakdown strength. Those properties resulted in superior energy storage properties. Oxygen-processed BCZT thin films showed an energy storage density (ESD) of 64.8 J cm(-3) and energy storage efficiency (ESF) of 73% at 2000 kV cm(-1) electric field. Apart from that, the films showed very low leakage current and improved polarization fatigue properties. Oxygen-processed virgin BCZT film displayed maximum polarization (P-max) of 106 mu C cm(-2) and P-r of 12.9 mu C cm(-2), whereas the measured P-max and P-r of the fatigued film after 10(10) switching cycles were 105 mu C cm(-2) and 13.2 mu C cm(-2) respectively. BCZT thin films with high ESD and ESF at 2000 kV cm(-1) electric field and with excellent fatigue properties could be considered as potential candidates for low and intermediate voltage ferroelectric energy storage applications

Ferroelectric and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 films in 200 nm thickness range

Lead-free piezoelectric Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCZT) thin films were fabricated on Si/SiO2/TiO2/Pt (100) substrates following chemical solution deposition technique. Microstructure of the nano-sized BCZT particles crystallized in the thin film was thoroughly characterized. Ferroelectric, dielectric and piezoelectric properties of the films were investigated in detail. The BCZT films annealed at 800 degrees C temperature exhibited high remanent polarization of 25 +/- 1 C/cm(2), energy density of 17 J/cm(3), dielectric constant of 1550 +/- 50 and dielectric tunability of 50%. Converse piezoelectric coefficients (d(33)) obtained from piezo-response force microscopy (PFM) measurements on BCZT grains of different grain size (20-100 nm) distributed on the BCZT 700 film varied widely from 90 to 230 pm/V. The same for BCZT 800 measured on different grain size (30-130 nm) varied from 120 to 295 pm/V. These BCZT thin films with high dielectric, ferroelectric, and piezoelectric properties might be good alternative to the PZT films for thin film piezoelectric device applications