Dielectric studies on MgTiO3 based composite ceramics and thin films for microwave applications

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There is a growing demand for new functional materials to enhance the performance of microwave devices due to rapid development in wireless communication technology. The composite approach is one of the versatile methods to obtain desired physical parameters in a single compound as natural compounds usually do not exhibit all requisite characteristics. The 0.9 MgTiO3- 0.1Ba5Nb4O15 composite ceramics exhibited a maximum relative density of 98% as well as suitable dielectric properties: dielectric constant (εr) ~20, loss tangent (tanδ) ~ 10-4, and quality factor (Q×fo) = 60,230 GHz at 8.25 GHz with τf ~ -5 ppm/oC for microwave resonator. The thickness-dependent structural, microstructural, and dielectric properties of 0.9MTO-0.1BNO thin films revealed improvement with an increase in film thickness. Further, the 0.96MgTiO3-0.04SrTiO3 composite ceramics exhibited the best microwave dielectric properties with moderate quality factor (Q × f0) ~ 26,154 GHz at 8.08 GHz and better thermal stability ~τf ~ 1.76 ppm/K are suitable for microwave communication applications as microwave filters, resonators, etc. The bilayer thin film of MTO and STO (STMT3) film exhibited excellent dielectric properties: loss tangent (1.89×10-3) and considerable dielectric constant ~65 at 10 GHz. Furthermore, the 0.7MgTiO3 – 0.3Ba0.5Sr0.5TiO3 composite ceramics exhibited high dielectric permittivity εr ~ 57, and quality factor, Q × f0 = 19,30 GHz at 4.16 GHz and τɛ ~54% and found to be promising for type -II capacitors in integrated circuits of de-couplers and filters. The bi-layer thin films of MTO and BST: MTO/BST and BST/MTO with alternate stacking order showed the role of stacking order. As per theoretical estimation, BST/MTO bilayer exhibited intermediate dielectric constant and loss (27.3 and~10-2) to BST, MTO monolayer whereas MTO/BST showed anomaly attributed to the generation of dipoles in the interface of individual layers at 100 kHz. Both MTO/BST and BST/MTO films exhibited tunable dielectric responses. These findings of this report provide perspective insight into the design of multilayer structured smart materials.
Supervisor: Dobiddi, Pamu
Dielectric Resonators, Dielectric Capacitors, Thin Films