Narrow Results

The preparing process and the properties of thick-film double-based thermo-sensitive material were studied. The preparing steps were as follows: (i) preparing Ba_1-xSr_xTiO₃ micro-powders with chemical co-precipitation method; (ii) adding dispersants and surface active agents into crushing medium powders to prepare Ba_1-xSr_xTiO₃ nanopowders; (iii) preparing V₂O₃-based micro-powders; (iv) mixing Ba_1-xSr_xTiO₃ nanopowders, V₂O₃-based micro-powders, donor impurities, acceptor impurities and micro additives according to a certain ratio to make thick-film thermo-sensitive ceramic material. The presintering and sintering temperature of the prepared PTC ceramics were both reduced, which is very meaningful in using cheaper SiC instead of more expensive MoSi₂, prolonging the kiln's life, and lowering the production cost. The samples we prepared did not contain PbO, so they are safe to the environment.

The study compares thick-film NTC thermistor devices, produced by the screen-printing (and firing) technique and by the Aerosol Deposition Method (ADM) at room temperature. The devices are compared with respect to film quality (optical, mechanical) and to the negative temperature coefficient of resistance (NTCR) parameters ${\rho }_{25}$ and $B$. While the screen-printed films are porous, the Aerosol Deposited (AD) films are characterized by high tightness, mechanical stability, and a production at room temperature. The electrical analysis shows that the AD films reach the ${\rho }_{25}$- and $B$-values of bulk NTCRs from literature after a moderate tempering step below 400${}^{\circ }$C in air. The screen-printed films show $B$-values that are comparable to the values of bulk NTCRs from literature and ${\rho }_{25}$-values that are significantly higher.