Plasma spraying enables to create layers with thickness in a millimeter range adhering on various substrates. This paper provides a study of electric and mechanical properties of BaTiO 3 coatings prepared by atmospheric plasma spraying. The spraying was carried out by a direct current gas-stabilized plasma gun. BaTiO 3 was fed into the plasma jet as a feedstock powder prepared by a reactive sintering of micrometer-sized powders of BaCO 3 and TiO 2 . Microstructure and phase composition are reported and discussed in connection with electric and mechanical properties. The ability of the used techniques to detect precisely the phase transformation temperatures of BaTiO 3 plasma sprayed coatings is discussed as well. A depth-sensing indentation measurement was done between 290 and 520 K to provide local mechanical characterization. The elastic modulus has shown slightly higher values than that reported typically in papers focused on BaTiO 3 ferroelectric thin films. The average Vickers microhardness is tested to characterize the samples in larger scale. A wear resistance in a slurry environment is reported as well. Dielectric properties are reported for the temperature window of existence of the tetragonal ferroelectric phase. Relative permittivity and loss factor are studied at frequency from 50 Hz to 1 MHz and temperature from 260 to 400 K. #

The relative permittivity and loss factor frequency dependence in a weak electric field of plasma sprayed perovskite and ilminite polycrystalline ceramic materials-pure synthetic calcium titanate, as well as magnesium titanate-calcium titanate mixture, were studied. It was observed that plasma-sprayed titanates exhibit a strong relaxation of permittivity and loss factor decrease when they are measured in an as-sprayed state. The frequency dependence of the earlier properties is influenced by chemical composition and spraying parameters, but the relaxation character in general is preserved in all cases. The volume resistivity of the samples in an assprayed as well as subsequently annealed state was studied also. Several aspects of the structural features of plasma deposits and their possible influence on dielectric properties are discussed. #

This paper presents the study of the dielectric properties of three plasma-deposited titanates. The deposits were prepared from powders with the same starting composition as industrially produced dielectric ceramics. Influence of plasma spraying itself and of the subsequent annealing of sprayed deposits on electric resistivity, permittivity and the loss factor is reported. Pure synthetic perovskite (CaTiO 3 ) and two perovskite-related ceramic materials (MgTiO 3 -CaTiO 3 and LaMg 0.5 Ti 0.5 O 3 -CaTiO 3 ) were plasma sprayed to form specimens enabling various electric measurements. CaTiO 3 and their solid solution with LaMg 0.5 Ti 0.5 O 3 have perovskite crystal structure and MgTiO 3 have the ilmenite structure. Water-stabilized plasma gun WSP 1 as well as commercial APS (gas stabilized system) were used to form ceramic layers on stainless steel substrates as well as self-supporting ceramic discs. Surface of specimens was ground after spraying. Thin layer of aluminum as the counter-electrode was sputtered in reduced pressure on the ground surface. Micrometric capacitor and ASTM-convenient resistivity adapter were used for voltage applying. Permittivity and volume resistivity were calculated from the measured capacity and resistance respectively. Self-supporting ceramic deposits were annealed at two different temperatures below and above the sintering temperature of the given material. Properties dependence on annealing temperature was obtained and discussed in relation to porosity. #

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