Co-firing Behavior And Theoretical Simulation Of Crystalizable Glass/Ferrite Composite Thick Films

The low temperature co-fired crystalizable glass powders (YF) and ferrite powders (HP) were used as research objectives. Sintering behavior of those two green tapes prepared by tape casting was studied as well as the co-firing behavior of the bi-layer laminates. Camber evolution, development of the sintering mismatch stress and microstructure of the co-fired laminates were revealed as a function of the heating rate and the thickness ratio of two layers. Theoretical model was then built up and a preliminary analysis of the evolution process was successfully achieved.Green tapes with controllable thickness and excellent performance were manufactured by the tape casting procedure using the chosen powders as raw materials. Densification behavior was measured for the two green tapes sintered freely at different sintering mechanism. Uniaxial viscosities of individual layers were determined through a vertical sintering technique by in-situ measuring shrinkage curves via an optical dilatometer. The results indicated that the uniaxial viscosities of the two materials showed a sharp increase when the density exceeded 0.85.Laminates with a total thickness of 900±10μm were manufactured and the thickness ratio of YF to HP was controlled to be 1:1. Co-firing behavior was explored for laminates sintered at three heating rates of 2℃/min,5℃/min and 10℃/min. The camber evolution was recorded and analyzed, followed by the calculation of the sintering mismatch stresses during the co-firing procedure utilizing the theoretical model. The causes for the discrepancy between the experimental results and the predictions of theoretical model can be summarized as the differences of the heating rate, the presence of anisotropic, parameters applied in the model and the sintering environment.Laminates with five thickness ratios of 2:1,1.75:1,1.5:1,1.25:1 and 1:1 were prepared, and the total thickness of all laminates was controlled to be 900±10μm. A heating rate of 5℃/min was applied and the co-firing behavior was recorded and analyzed during the co-firing process. The sintering mismatch stresses were calculated according to the theoretical model and impacts of the thickness ratio on the camber evolution and sintering mismatch stress development were also explored. Differences between the experimental results and theoretical predictions were analyzed and then demonstrated by the microstructures of different laminates.A theoretical model for the sintering mismatch stress distribution in the thickness direction and the evolution law was established for bi-layer laminates during a co-firing process. A comparison between the simulated results and calculated results through the existing model was conducted, indicating a good applicability during the initial and intermediate stages of the co-firing procedure. Microstructures for the co-fired laminates were applied to explore and examine the accuracy of the model.