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The Na 2 O–K 2 O–Nb 2 O 5 –SiO 2 glass matrixes modified by alkaline-earth metals oxide MO (M = Ca2+, Sr2+ and Ba2+) with different field strength (F s) are prepared. The degree of polymerization (DOP) of the glass network structure is enhanced with the addition of MO. The (35- x)Na 2 O–5K 2 O–40Nb 2 O 5 –20SiO 2 - x MO glass are crystalized at the exothermic peak 916 °C as evidenced by an exothermic peak in thermal analysis. The crystallization kinetics are analyzed by crystallization activation energy (E c) which increases with the addition of MO facilitating the homogenous nucleation. The crystallinity and the fraction of crystalline phase of the glass-ceramics are analyzed by structural refinements. The dielectric permittivity and polarization of the glass-ceramics are researched. The electrical homogeneity of glass-ceramics is discussed on different scales. On the grain scale of the glass-ceramics, the uniform microstructure prevents the free charge from accumulating. On the glass network scale, the tight glass network structure prevents large interface polarization caused by the accumulating of space charge. A large binding energy (W) or minimum hopping distance (R m) prevents the electrons from hopping. Kelvin probe force microscopy (KPFM) is used to test the potential of the interface polarization as direct evidence of the electrical homogeneity. The magnitude of the breakdown strength (BDS) of the glass-ceramics is affected by the electrical homogeneity of the glass-ceramics. The average value of BDS is 1780 kV/cm for the Na 2 O–K 2 O–Nb 2 O 5 –SiO 2 –BaO glass-ceramics. The maximum potential energy storage density of 23.1 J/cm3 is obtained for the Na 2 O–K 2 O–Nb 2 O 5 –SiO 2 –BaO glass-ceramics with x = 3. [ABSTRACT FROM AUTHOR]

Ba 0.4 Sr 0.6 TiO 3 (BST) powders were prepared by hydrothermal method, the ceramics were sintered in N 2 , air and O 2 atmosphere respectively. The effect of sintering atmosphere on the microstructure, dielectric properties, and energy storage performance of BST ceramics were investigated. The grain size of the BST ceramics sintered in O 2 atmosphere was reduced to 0.44 µm, indicating the grain growth was significantly inhibited with increasing oxygen partial pressure due to the lack of oxygen vacancy. Dielectric relaxation behavior was observed in the BST ceramics, and the degree of which was increased with increasing oxygen partial pressure. BST ceramics sintered in O 2 atmosphere showed the largest critical breakdown strength of 16.72 kV/mm, at which the highest energy storage density of 1.081 J/cm 3 and a moderate energy storage efficiency of (73.78%) were obtained. The dependence of energy-storage properties on applied field was also investigated, it was found that the energy storage density increased with increasing applied filed while the energy storage efficiency decreased with increasing applied filed. [ABSTRACT FROM AUTHOR]