G Processing and characterization of CaTiO 3 perovskite ceramics
Calcium titanate (CaTiO3) ceramics with perovskite structure were produced by solid state reaction. Calcium carbonate (CaCO3) and titanium dioxide (TiO2) were mixed (in molar ratios 1/1 and 3/2), and the obtained mixtures were calcined at 1150 °C in successive thermal cycles. The obtained samples were characterized by differential thermal analysis, thermogravimetry, X-ray diffraction, measurement of particle size distribution and linear thermal shrinkage. XRD results indicated that the samples have perovskite CaTiO3 structure with small amount of secondary CaO and TiO2 phases, and their phase composition depends on the heat treatment conditions. The measured values of electrical resistivity were within the characteristic range of insulating materials and approach values corresponding to semiconducting ceramics.
Negative Temperature Coefficient Resistance of CaTiO3 for Thermistor Application
Present research presents CaTiO3 as an important negative temperature coefficient resistance (NTCR) thermistor material. Two routes were adopted such as solid state reaction and high energy ball milling (HEBM) for comparative analysis. X-ray diffraction (XRD), and Steinhart–Hart equation used for characterization of material formation and thermistor property. XRD pattern shows single phase orthorhombic symmetry or both samples. Electrical resistance found by LCR meter shows about NTCR behaviour and Steinhart–Hart model provides information for its suitability towards thermistor industry. To know the faster response nature time domain analysis performed on both samples. To the best knowledge, there are not much data available on properties of CaTiO3 as thermistor based temperature sensor material, which lead this research work. Enhanced sensing behaviour observed in CaTiO3 processed through HEBM. Both the samples signifies their strong potential in thermistor industry with sensitivity in the range of 4000–6700 K with exponential electrical resistance change in the specified temperature range.
Thermal decomposition of titanyl oxalates IV. Strontium and calcium titanyl oxalates
Abstract Thermal decomposition of strontium titanyl oxalate tetrahydrate and calcium titanyl oxalate hexahydrate have been studied employing TG, DTA, gas and chemical analysis. The decompositions proceed through three major steps: dehydration, decomposition of the oxalate to a carbonate and the decomposition of the carbonate to yield the final products, the metatitanates. The intermediates of the oxalate decomposition are found to be Sr 2 Ti 2 O 4+x (CO 3 ) 2 -x(CO 2 ) x and Ca 2 Ti 2 O 4 (CO 3 ) 2 , respectively. The entrapment of carbon dioxide in the former and the presence of non-equivalent carbonate groups in the latter are substantiated by their i.r. spectra. The penultimate solid residues are poorly crystalline Sr 2 Ti 2 O 5 CO 3 and amorphous Ca 2 Ti 2 O 5 CO 3 . Decompositions of these carbonates are accompanied by growth in particle size of the products, SrTiO 3 and CaTiO 3 , respectively.