Optical transmittance and energy storage properties of potassium sodium niobate glass-ceramics

In this work, 0.8(K₂O-Na₂O-2Nb₂O₅)−0.2((1-x)B₂O₃-xP₂O₅) (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) glass-ceramics have been fabricated. The effects of P₂O₅ on the microstructure and properties of the glass-ceramics were comprehensively studied. The addition of P₂O₅ promotes the transition of the glass network structure from a negatively charged [B∅₄]^- tetrahedron to an electrically neutral [BP∅₄] tetrahedron. With the increase of P₂O₅ content, the formation of K₂B₄O₇ is inhibited, with major phase of Na_0.9K_0.1NbO₃ and minor phase of K₂B₄O₇. It is found that the band gap width of the glass-ceramics increases from 3.34 eV to 3.52 eV firstly and then decreases to 3.43 eV. The grain size of the glass-ceramics decreases from 150 nm to 50 nm. High optical transmittance (63%), large discharge energy density (4.58 J/cm³) and large energy storage efficiency (98%) have been simultaneously obtained for K₂O-Na₂O-Nb₂O₅-B₂O₃-P₂O₅ glass-ceramics, which are potential for the applications of the transparent pulse capacitors.