The Study Of CaTiSiO₅-based High-frequency Dielectric Ceramics Synthesized By Laser Technology

The high frequency dielectric ceramic materials has a very important position in modern functional ceramic materials, With a wide range of uses. Undering the high-frequency (1MHz) conditions The high frequency dielectric ceramic materials have low dielectric loss, wide range temperature coefficient of dielectric constant. It is widely used in ceramic capacitors dielectric. According to the temperature coefficient of dielectric constant It can be divided into two categories.One is the capacitor dielectric ceramic materials for thermal compensation,The capacitor dielectric ceramics of thermal compensation has a large negative temperature coefficient of dielectric constant.For example CaTiO3,TiO2 and so on.The capacitor dielectric ceramics of thermal compensation are used in the oscillator circuit into loop to compensate the positive temperature coefficient of inductance components, so that the resonant frequency circuit to maintain the same or little change.The other is thermally stable capacitor dielectric ceramics, It has a very small temperature coefficient of dielectric absolute value of the number, Such as TiO2-CaTiSiO5,CaTiO3-CaTiSiO5,CaTiO3-Ca(Mg1/3Nb2/3)O3,SrZrO3-SrTiO3,CaTiO3-CaZrO3 and so on.The thermally stable capacitor dielectric ceramics are widely used in mobile communications, satellite communications, precision instruments and military radar and other fields.The CaTiO3-CaTiSiO5 dielectric ceramic is an excellent high-frequency dielectric ceramics, It is monoclinic CaTiSiO5 (εr≈40, tanδ≈5×10-4,αε≈+1200×10-6/℃) and orthogonal CaTiO3 (εr≈40, tanδ≈5×10-4αε≈+1200×10-6/℃) two phases, It has a more excellent dielectric properties(εr≈82, tanδ≈4×10-4,αε≈±25×10-6/℃), Thus a growing concern. By the appropriate molar ratio (0.82:0.18) of compound TiO2 and CaTiSiO5 was also able to obtain a composite dielectric properties of composite materials, That has a high dielectric constant, low dielectric loss and near-zero temperature coefficient of dielectric constant.Also with the rapid development of modern communication technology, Ceramic capacitors toward small, high-capacity areas direction.what's more, the dielectric ceramics of large dielectric constant and dielectric small loss is a prerequisite to create high-performance ceramic capacitors. Therefore, improving the dielectric properties of CaTiO3-CaTiSiO5,(CaTiSiO5)0.18(TiO2)0.82 dielectric ceramics is to broaden the scope of application of ceramic CaTiO3-CaTiSiO5,(CaTiSiO5)0.i8(TiO2)0.82 pressing issue. In recently years, laser sintering technology in the preparation of new materials and improve material performance shows a unique advantage. This work is the preparation of CaTiO3-CaTiSiO5 (CaTiSiO5)0.18(TiO2)0.82 dielectric ceramics using of laser sintering technology, and its preparation has been systematically studied. The lattice structure, chemical composition, microstructure, dielectric properties and so on were measured and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), precision impedance analyzer, Raman scattering et al measurement.According to the physical properties and microstructure of the sample, The optimum technology of CaTiO3-CaTiSiO5, (CaTiSiO5)0.18(TiO2)0.82 dielectric ceramics by laser sintering were:Laser power 1.2 kW, defocus 90 mm, the sintering time 140s; laser power 1.0 kW, defocus 140 mm, sintering time 240s. CaTiO3-CaTiSiO5 dielectric properties of ceramic samples comparing with the high temperature furnace sintered, dielectric constant increased to 376 from 82 which the sample sintered by the furnace, dielectric loss and temperature coefficient basically unchanged. The microstructure changed significantly, the sample was dense without a large number of pores and micro-cracks, the grain was large and grew integrallty and alignmently, these grains connected each other and formed dendritic structure group. The density and purity of (CaTiSiO5)0.18(TiO2)0.82 dielectric ceramics are perfect, the sintered sample showed lath-shaped microstructure formed by regular growth with the laser beam in the opposite direction, which is beneficial to the improvement of dielectric properties. Among the techniques for formation of functional ceramics, compared with other orientated growth technology, the laser sintering technology is simple operation, strong orientated growth of grain, high efficiency, density and purity.