Bulk c-oriented CeF₃ single crystals (sp. gr. $P\overline{3}c1$) were grown successfully by the vertical Bridgman technique in a fluorinating atmosphere. A description of the crystal growth procedure and the solution of the difficulties during the growth process are presented in detail. The anisotropy of the mechanical, thermal and electrophysical properties were studied for the first time. The maximum values of the thermal conductivity coefficient (α = 2.51 ± 0.12 W·m⁻¹·K⁻¹) and the ionic conductivity (σ_dc = 2.7 × 10⁻⁶ S/cm) at room temperature are observed in the [0001] direction for the CeF₃ crystals. The Vickers (H_V) and Berkovich (H_B) microhardnesses for the $(0001)$, $(10\overline{1}0)$ and $(11\overline{2}0)$ crystallographic planes were investigated. The H_B values were higher than the H_V ones and decreased from 3.8 to 2.9 GPa with an increase in the load in the range of 0.5–0.98 N for the hardest $(0001)$ plane. The $\left\{11\overline{2}0\right\}$, $\left\{10\overline{1}0\right\}$ and $\left\{0001\right\}$ cleavage planes were observed during the indentation process of the CeF₃ crystals. The variability of Young’s, the shear modules and Poisson’s ratio were analyzed. A significant correlation between the shapes of the Vickers indentation patterns with Young’s modulus anisotropy was found. The relationship between the anisotropy of the studied properties and the features of the CeF₃ trigonal crystal structure is discussed.

ScF₃ optical quality bulk crystals of the ReO₃ structure type (space group $Pm\overline{3}m$ , a = 4.01401(3) Å) have been grown from the melt by Bridgman technique, in fluorinating atmosphere for the first time. Aiming to substantially reduce vaporization losses during the growth process graphite crucibles were designed. The crystal quality, optical, mechanical, thermal and electrophysical properties were studied. Novel ScF₃ crystals refer to the low-refractive-index (n_D = 1.400(1)) optical materials with high transparency in the visible and IR spectral region up to 8.7 µm. The Vickers hardness of ScF₃ (H_V ~ 2.6 GPa) is substantially higher than that of CaF₂ and LaF₃ crystals. ScF₃ crystals possess unique high thermal conductivity (k = 9.6 Wm⁻¹К⁻¹ at 300 K) and low ionic conductivity (σ = 4 × 10⁻⁸ Scm⁻¹ at 673 К) cause to the structural defects in the fluorine sublattice.

The symmetry (sp. gr.I \(\bar 4\) 3d) and lattice parameters have been determined for the first time for Cs₅(H₂SO₄)₂(H₂PO₄)₃ crystals in the temperature range from 172 to 390 K. The thermal and optical properties of crystals, as well as their conductivity, have been investigated at elevated temperatures. It is shown that a crystal heated to T = 365 K undergoes a phase transition with symmetry lowering to the tetragonal phase (with the parameters a = 4.965(1) Å and c = 5.016(1) Å), while at T ≈ 390 K a phase transition to the cubic phase is presumably observed. With a decrease in temperature, a phase transition without a change in symmetry occurs at T = 240 K.