Dielectric Properties of Fine‐Grained Barium Titanate Based X7R Materials

Abstract

The next generations of multilayer ceramic capacitors are expected to have active ceramic layer thicknesses of 3 µm or less. To retain a reliable ceramic device, it is advantageous to engineer a uniform and fine-grained microstructure. In this study, a dense ceramic (>96% of theoretical) with finegrained size (<0.2 µm), and permittivity of 2800, meeting the EIA X7R temperature characteristic has been obtained using hydrothermally synthesized BaTiO 3 powder with precipitation-coated additives. The temperature coefficient of capacitance (TCC) and the dissipation factor (DF) are investigated as a function of active layer thickness and compared with that of a conventional coarse-grained dielectric of similar composition and fired density. The fine-grained ceramic maintained X7R characteristic in active layers as thin as 3 µm under 1 V AC and 1 kHz test conditions. For equivalent active thickness, the DF of the fine-grained version was consistently lower than the coarse-grained material. These results indicate that an improved voltage coefficient is possible for finer-grained materials under otherwise equivalent conditions. The possible causes for this behavior are also discussed.

Enhanced dielectric and ferroelectric characteristics in Ca-modified BaTiO3 ceramics

“…[1][2][3][4] It is well known that BaTiO 3 undergoes the successive phase transitions from cubic to tetragonal (C-T), tetragonal to orthorhombic (T-O), and orthorhombic to rhombohedral (O-R), and its dielectric response and ferroelectricity primarily originate from the displacement of Ti ions, whereas the interaction of Ba in A-site and oxygen is ionic, which has no ferroelectric active component. 5,6 On the other hand, to improve the device performance and meet the continuing demand for further miniaturization of electronic devices using BaTiO 3 based materials, it is important to ensure the high dielectric constant, low dielectric loss, high remanent polarization and high dielectric strength.…”

Effects of Oxide Additives Coating on Microstructure and Dielectric Properties of BaTiO3

“…Although in recent years numerous research works have been conducted about ceramic coating, there are few studies about additives coated BaTiO 3 particles [19][20][21][22]. Bruno and Swanson studied chemical coating of additives for X7R/Y5V formula and reported electrical properties [19].…”

Microstructural Analysis of X7R-Type BaTiO3 Multilayer Ceramic Capacitors (MLCCs)

“…Conventionally, BaTiO 3 -based dielectrics have been used in MLCCs, and in order to produce thinner dielectric active layers the average grain size of the BaTiO 3 must be reduced. The dielectric constant of BaTiO 3 is dependent on the grain size of the material [2,[5][6][7][8]. Moreover, electrode migration into the dielectric layers, which can affect the stability and dielectric properties of MLCCs, has to be considered as this is more likely to occur in systems with thinner active dielectric layers.…”

“…The keys to achieving these objectives are to reduce the thickness of the metal electrode and dielectric layers, to develop high permittivity dielectric materials and to utilize inexpensive internal electrodes and terminals [2][3][4].…”