Single crystals of (NH₄)₃HfF₇ were grown. Polarising optical observations as well as measurement of the heat capacity and birefringence Δn(Т) were performed in the temperature range of 200–310 K. Reversible phase transitions at temperatures T₀ = 290 K, Т₁ = 280.5 K, Т₂ ≈ 273 K, Т₃ = 266 K, Т₄ = 259 K, Т₅ = 231 K, Т₆ = 229 K were found. Observations in polarised light make it possible to suggest a sequence of changes in the symmetry groups for these transitions: $Fm{\displaystyle \overline{3}}m$ ⟵Т₀→ cub. ⟵Т₁→ mmm (1) ⟵Т₂→ mmm (2) ⟵Т₃→ mmm (3) ⟵Т₅→ 2/c. The T-p phase diagram was studied and the temperature boundaries of the stability of the distorted crystalline phases were determined. A significant change of the entropy at successive phase transitions ΣΔS = 10.6 J/mol K indicates a disordering of the initial cubic phase.

生长（NH ₄）₃ HfF _7的单晶。偏振光学观测以及热容量和双折射率Δn（Т）的测量是在温度范围为200-310 K.可逆相变在内的温度T执行₀  = 290 K，Т ₁  = 280.5 K，Т ₂  ≈273 K，Т ₃  = 266 K，Т ₄  = 259 K，Т ₅  = 231 K，Т ₆  = 229 K含量找到。在偏振光中的观察可以为这些过渡建议对称组的一系列变化：$F米{\displaystyle \overline{3}}米$⟵Т ₀ →幼崽。⟵Т ₁ →MMM（1）⟵Т ₂ →MMM（2）⟵Т ₃ →MMM（3）⟵Т ₅ →2 / C。研究了Tp相图，并确定了畸变结晶相稳定性的温度边界。在连续相变ΣΔS= 10.6 J / mol K时，熵的显着变化表明初始立方相无序。