Phase Transitions in the System BaTiO3-KnbO3

Abstract

Solid solution formation in the systemBaTiOr gabor was established by X-ray diffraction and dielectric measurements. Solid solutions with cubic symmetry were observed in the composition range from 4 to 90 mole yo I u y b o a at room temperature. The lattice parameter for the BaTiOp solid solutions increased with increasing -boa;that for the KNbOa solid solutions decreased with the addition of BaTiOa. A distinct discontinuity in lattice parameter was observed at the composition containing about 65 mole yo BaTiOs. Dielectric measurements were made from -195O to 400OC. The cubic-tetragonal transition temperature of BaTiOs was rapidly lowered with increasing addition of KNb03, whereas the two lower phase transition temperatures were raised. All three phase transitions of KNbOI were rapidly lowered with increasing addition of BaTi08. The observed phase transitions, lattice parameters, and electron probe data suggest a complex region in the subsolidus which extends from 35 to about 75 mole % KNb03.

Viscoelastic, dielectric, and thermal properties of BaTiO3‐3%KNbO3

“…Given the existence of hysteresis in a first order phase transition, the transition temperature is expressed in the phase diagram as the average of the transformation temperatures, i.e., the peak temperatures of the transformation, during a heating and a cooling trend. The transition temperatures of the ''as-prepared'' samples in the present study have been compared with the published data of the KNbO 3 -BaTiO 3 phase diagram by Bratton [6], as shown in Fig. 3.…”

“…3. In that study, the transition temperatures were obtained from maximums on the dielectric constant-temperature curves [6]. Figure 4 shows the temperature dependence of the dielectric constant of 3%KNbO 3 -BaTiO 3 at 10 kHz in both heating and cooling (0.01 8C/s).…”

“…The Curie point of BaTiO 3 shifts to lower temperature by introducing certain kind of dopant, such as KNbO 3 , BaZrO 3 , BaSnO 3 , etc (a phase diagram of the KNbO 3 -BaTiO 3 system [6] is shown in Fig. 3).…”

Control of Interfacial Structure of Potassium Niobate-Barium Titanate Ceramics and Their Dielectric Properties

“…Recently, the high piezoelectric properties have been reported for a BT/KN composite and they were explained to be attributed to the interfaces between tetragonal BT grains and orthorhombic KN grains [2]- [4],.The transmission electron microscopy (TEM) observation revealed that the interfaces were consisted of Ba-rich tetragonal grains and KN-rich orthorhombic grains [5]. Because both KN and BT grains remained for the composite, it is expected that the temperature dependence of the dielectric constant is a simple summation of the two, making it attractive high temperature dielectrics with high permittivity induced by the interfaces.…”

Phase diagram of (Na0.5K0.5)NbO3-(Bi0.5Na0.5)ZrO3 solid solution

“…In increasing the volume of the unit cell, introducing BZ to NKN acts in a similar way as negative physical pressure, 15,16 and the increase of T OÀR could be understood. However, in the NKN-xBNZ solid solution, V p decreases, a behavior not in consistent with that under a negative physical pressure, T OÀR increases as well.…”