Integrated SnO 2 : CuO thin-film based H 2 S gas sensor has been realized using low temperature co-fired ceramics (LTCC) tapes with heater and thermister buried inside the LTCC multilayer structure. The SnO 2 : CuO thin films are deposited on top of the structure. At operating temperature of 180°°°°C, these films revealed sensing properties very similar to the reference films deposited on Alumina substrates. Further, effect of operating temperature on sensitivity was studied and sensor films on LTCC substrate were found to detect H 2 S with maximum sensitivity at a lower operating temperature of 100°°°°C.The developed sensors have been tested for a period of more than one year and found to show a stable response.
M-type barium hexaferrite (BaFe O ) is investigated with an aim of using with low temperature co-fired ceramic (LTCC) substrate material. The as-calcined powders from combustion synthesis at neutral and acidic precursor solutions are used, which exhibit excellent properties of low coercive field values (up to 1350 Oe) and high magnetization (up to 60 emu/g). With an appropriate amount of Bi O as sintering aid, high density ferrites have been realized at LTCC processing temperatures. The sintered ferrites possess bulk resistivity in excess of cm, indicating their suitability for high-frequency applications. Complex magnetic permeability and magnetic loss factors are studied up to 1 GHz frequency. Complex permeability between 1.2 to 2.2 and magnetic loss tangent between 0.05-0.5 have been realized for the sintered ferrites. The influence of Bi O content on resistivity and high-frequency magnetic properties is discussed. It is observed that the sample prepared by employing neutral pH during combustion preparation and calcined at 1200 C for 12 h shows low coercivity of 1350 Oe. After sintering at 900 C with 2 wt% Bi O , the sample shows better results with permeability of 1.5-1.7, magnetic loss tangent below 0.3 up to 700 MHz frequency and a high resonance frequency of 140 and 715 MHz in VHF and UHF band, respectively. Since the synthesis conditions provide better control over basic magnetic properties, the use of combustion synthesized BaFe O material augers well for magnetic materials applications in LTCC technology.Index Terms-Barium hexaferrite, LTCC, non-reciprocal devices, permeability, VSM.
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