Czaja Piotr, Szostak Elżbieta, Hetmańczyk Joanna, Zachariasz Piotr, Majda Dorota, Suchanicz Jan, Karolus Małgorzata, Bochenek Dariusz, Osińska Katarzyna, Jędryka Jarosław, Kityk Andriy, Piasecki Michał
Institute of Technology, University of the National Education Commission, Podchorążych 2, 30-084 Krakow, Poland.
Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland.
Materials (Basel). 2024 Apr 29;17(9):2089. doi: 10.3390/ma17092089.
Lead-free KBiTiO (KBT) ceramics with high density (~5.36 g/cm, 90% of X-ray density) and compositional purity (up to 90%) were synthesized using a solid-state reaction method. Strongly condensed KBT ceramics revealed homogenous local microstructures. TG/DSC (Thermogravimetry-differential scanning calorimetry) techniques characterized the thermal and structural stability of KBT. High mass stability (>0.4%) has proven no KBT thermal decomposition or other phase precipitation up to 1000 °C except for the co-existing KTiO impurity. A strong influence of crystallites size and sintering conditions on improved dielectric and non-linear optical properties was reported. A significant increase (more than twice) in dielectric permittivity (), substantial for potential applications, was found in the KBT-24h specimen with extensive milling time. Moreover, it was observed that the second harmonic generation (λ = 532 nm) was activated at remarkably low fundamental beam intensity. Finally, spectroscopic experiments (Fourier transform Raman and far-infrared spectroscopy (FT-IR)) were supported by DFT (Density functional theory) calculations with a 2 × 2 × 2 supercell (4 symmetry and C4v point group). Moreover, the energy band gap was calculated ( = 2.46 eV), and a strong hybridization of the O-2 and Ti-3 orbitals at explained the nature of band-gap transition (Γ → Γ).
采用固态反应法合成了具有高密度（约5.36 g/cm³，90%的X射线密度）和成分纯度（高达90%）的无铅KBiTiO₃（KBT）陶瓷。高度致密的KBT陶瓷呈现出均匀的局部微观结构。热重/差示扫描量热法（TG/DSC）技术表征了KBT的热稳定性和结构稳定性。高质量稳定性（>0.4%）表明，除了共存的KTiO杂质外，在高达1000℃时KBT没有热分解或其他相析出。据报道，微晶尺寸和烧结条件对改善介电和非线性光学性能有强烈影响。在具有较长球磨时间的KBT-24h样品中，发现介电常数（ε）显著增加（超过两倍），这对于潜在应用具有重要意义。此外，观察到在极低的基波强度下二次谐波产生（λ = 532 nm）被激活。最后，通过2×2×2超胞（4种对称性和C₄ᵥ点群）的密度泛函理论（DFT）计算支持了光谱实验（傅里叶变换拉曼光谱和远红外光谱（FT-IR））。此外，计算了能带隙（Eg = 2.46 eV），并且在Γ点处O-2和Ti-3轨道的强杂化解释了带隙跃迁（Γ→Γ）的性质。
