Bulk Growth, Thermal, and Polarized Spectral Characters of Nd³⁺‐Doped Ca₃(BO₃)₂ Single Crystals

Abstract The growth, ion concentrations, powder X‐ray diffraction, thermal properties, and optical spectroscopy of Nd 3 ⁺‐doped Ca₃(BO₃)₂ single crystals are investigated. The Nd 3+ ‐doped Ca₃(BO₃)₂ single crystals with 1.97 at.% Nd 3 ⁺ are successfully grown using the Czochralski (Cz) technique. To address the chemical valence imbalance between Nd 3 ⁺ and Ca 2 ⁺ in the Ca₃(BO₃)₂ crystals, the Na⁺ ions are introduced. The concentrations of Nd 3 ⁺ and Na⁺ ions in the as‐grown crystals are measured using inductively coupled plasma atomic emission spectroscopy (ICP‐AES), yielding concentrations of 1.97 at% (N 0 = 1.55 × 10 20 cm −3 ), 1.94 at% (N 0 = 1.52 × 10 20 cm −3 ), respectively. The thermal behavior of the Nd 3 ⁺‐doped Ca 3 (BO 3 ) 2 crystals, including thermal expansion coefficients, specific heat, and thermogravimetric and differential thermal analysis (TG‐DTA), is systematically investigated. At room temperature, the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay lifetimes are measured. Spectral parameters, including polarized absorption and stimulated emission cross‐sections, intensity parameters, transition probabilities, radiative lifetime, and branching ratios are determined using the Judd‐Ofelt (J‐O) theory. The results indicate that Nd 3+ ‐doped Ca 3 (BO 3 ) 2 crystals are promising materials for near‐infrared lasers, offering advantages such as rapid growth, large size, high specific heat, strong emission, and environmental stability.