Phase formation, dielectric and ferroelectric properties of CaxBa1−xNb2O6 ceramics

Role of structural modulation in electrical properties of tungsten bronze (Ca0.28Ba0.72)2.5−0.5Na Nb5O15 ceramics

“…In our previous work [22], effects of Ca/Ba ratio on the phase formation, microstructure, dielectric and ferroelectric properties of CBN ceramics were systemically studied. It was found that the ceramics with the highest density, most homogeneous microstructure, and optimized properties were obtained at x = 0.28.…”

Structural modulation and electrical properties in ferroelectric niobates (Ca0.28Ba0.72)2.5−0.5K Nb5O15 (0.0≤x≤0.6) ceramics

“…The variations of tanδ with temperature for all CBKN ceramics show similar trend, that is, all samples show weak tanδ peaks below T c . This phenomenon is generally observed in ferroelectrics and can be attributed to the improvement of the domain wall during the ferroelectric to paraelectric phase transition [19,26]. Above T c , the monotonous increase in tanδ can be attributed to the scattering of thermally activated charge carriers and some defects in the samples [26].…”

“…The ions-occupying-situation in different tunnels of A1 and A2 sites associated with K + concentration can affect the distortion of NbO 6 octahedron polar unit and result in some characteristic dielectric and ferroelectric behavior, which will be discussed subsequently. [19]. The amount of anisometric pillar-type grains increases and the equiaxed shape grains decreases with increasing x.…”

“…Then the TTB structure with only five A-sites are occupied out of six and it results in a socalled 'unfilled' structure that is responsible for charge disorder and relaxor behavior [12,14,16]. In our previous work, the CBN ceramics with the highest density and optimized properties were obtained at x = 0.28 by the conventional solid state method [19]. Afterwards, introducing alkali Na + ions (1.39 Å) with similar radius of Ca 2+ ions in CBN28 to decrease the structural vacancies has resulted in the enhancement of dielectric and ferroelectric properties.…”

“…Though much work about recent TTB materials has been directly focused on the CBN niobates, they mainly discussed the effects of Ca/Ba ratio [10,19] or doping oxides [2] on dielectric properties, relaxor ferroelectric characteristics, and also elastic behavior of CBN crystals or ceramics.…”