Exploratory growth and characterization of CaNdAl3O7 single crystal with nonsymmetric structure in tetragonal family

The new component of melilite type crystal CaNdAl₃O₇ (CNA) was grown by the Czochralski pulling method. Single crystal structure analysis was conducted. It is found that the CNA crystal belongs to the tetragonal system with P-42₁m space group. The cell parameters a = b = 0.77461 nm and c = 0.51089 nm. The density and Mohs hardness of CNA crystal are 4.08 g/cm³ and 5.45, respectively. The specific heat of the crystal is 0.57–0.77 J/(g·K) in the temperature range of 30–300 °C. X-ray photoelectron spectroscopy (XPS) shows that the crystal has stable atomic valence states and chemical environment. The vibration state of polyhedra groups in the crystal was measured by Raman spectra, and the piezoelectric response was analyzed based on the calculated results for the polyhedra polarization dipole moments. The relative dielectric permittivity of the CNA crystal at room temperature was determined to be 11.80 and the electrical resistivity was measured to be on the order of 5 × 10⁶ Ω·cm at 800 °C.