Rajnish Kurchania

Oxygen Potential in Molten Tin and Gibbs Energy of Formation of SnO 2 Employing an Oxygen Sensor

On-line monitoring of the dissolved impurities in molten metals is important for better process control during alloying and metal refining operations. Disposable-type oxygen sensors are commercially available and are used in the iron and steel industry worldwide. However, there is a need for developing low-cost, reliable, long-life oxygen sensors for continuous monitoring of dissolved oxygen in molten metals. In this paper we present the results of the physical and electrical characterization of the solid electrolyte material ZrO 2 (8 mol%Y 2 O 3 ). The experimental results of the application of long-life solid-state electrochemical sensors designed using yttria-stabilized zirconia solid electrolyte for the measurement of oxygen potential in molten tin between 823 to 1273 K and standard Gibbs energy of formation of SnO 2 from its elements are also reported.

Effect of Niobium Modifications to PZT (53/47) Thin Films Made by a Sol-Gel Route

Niobium-modified lead zirconate titanate thin films (PNZT) with nominal compositions, Pb(1−0.5x) (Zr0.53 Ti0.47)1−x NbxO3:x = 0.02–0.07, have been prepared using a diol based sol-gel route. Single-layer (0.5 μm) films were fabricated on platinised silicon substrates by spin-coating. The effect of niobium additions with regard to phase development, microstructure, and ferroelectric and dielectric properties were investigated for different annealing temperatures. For comparison, unmodified PZT films were also prepared. Niobium substitution increased the crystallisation temperatures for perovskite PNZT phase formation. The values of remanent polarisation Pr and dielectric constant εr were found to decrease with the introduction of Nb. For example, in films heated at 700°C for 15 min, the Pr value of an unmodified PZT film was 31 μC cm−2, compared to 17 μC cm−2 for an x = 0.05 PNZT film, whilst respective relative permittivity values fell from 1190 to 600. The highest Nb concentration film, x = 0.07, did not display any switchable polarisation characteristics, which is consistent with high levels of intermediate pyrochlore phase.

An investigation of BST:MgTiO/sub 3/ and X7R:MgTiO/sub 3/ based ceramics for microwave applications

There is a growing demand for dielectrics with field tunable permittivity for use in frequency agile filters and phase shifters at microwave frequencies. The paraelectric phase composition of barium strontium titan a to (BST) is a popular choice because of its non-linear properties demonstrated by the field dependence of permittivity. However, the dielectric properties of BST compositions are temperature dependent, and thereby compromise the tunability. In this paper the dielectric properties of temperature stable X7R dielectrics (/spl Delta/C < 15% for -55/spl deg/C < T < 125/spl deg/C), BST and their composites with magnesium titanate (MT) have been investigated to determine their field dependent tunability. Magnesium titanate is a low permittivity material has been used to attenuate the relative permittivity and lower the dielectric loss of BST and X7R for microwave frequency applications. A series of (1-x)BST:MT and (1-x)X7R:MT composites have been synthesized (x=0.0 to 0.5), at sintering temperature ranging from 1200/spl deg/C to 1400/spl deg/C. Structural characterization of these composites have been carried out and their dielectric permittivity was measured as a function of temperature and DC bias field.

Intermodulation distortion in wide-band dual-mode bulk ferroelectric bandpass filters

An investigation into intermodulation (IM) distortion in bulk ferroelectric bandpass filters is presented. The main objective has been to study the effect of the response time of ferroelectric material on IM distortion. In order to investigate the response, time IM measurements with wide carrier frequency spacing must be performed. Thus a novel planar dual-mode bandpass filter, with 600 MHz bandwidth at 2 GHz, has been designed and fabricated on a bulk Barium Strontium Titanate (BST) substrate. The two tone third-order IM has been measured for a range of signal separations in order to estimate the material response time.

Characterization of sol-gel derived PZT and PLZT thin films

Lead zirconate titanate (PZT) and lead lanthanum zirconate titanate (PLZT) precursor sols were prepared using a diol based sol-gel route. Thin films were deposited by spin coating onto PtrTi/SiO/sub 2//Si substrates. The effects of lanthanum incorporating up to 10 mol% lanthanum to the base PZT 53/47 composition, and the effects of firing temperature (500-700/spl deg/C) on crystallization, microstructure, ferroelectric and dielectric properties have been investigated. Films fired at 700/spl deg/C for 15 minutes with 0, 2 and 5 mole percent lanthanum levels had values of remanent polarization of 31, 23 and 14 /spl mu/C cm/sup -2/ (at 300 kV cm/sup -1/, 60 Hz) and corresponding relative permittivity values of 1485, 830 and 700 respectively.