Crystal structure evolution and temperature-dependent phase transition of solid solutions are much desired for the understanding of the optimization of functional properties. Herein, the NASICON-type NaZr₂(PO₄)₃–SrZr₄(PO₄)₆ solid solutions with the formula Na_(2−2x)Sr_x[ ]_xZr₄(PO₄)₆ (0 ≤ x ≤ 1), where [ ] represents the vacancy, were prepared by the sol–gel method, and their crystal structures, phase transitions and thermal expansion properties were investigated in detail. In the range of x = 0.3–0.35, there is a reversible structural phase transition Rc ↔ R and the different structural models of the R phase and Rc phase were built to better understand the phase transition mechanism. We determined the phase transition boundary between the Rc and R structures and predicted the phase transition temperature of Na_(2−2x)Sr_x[ ]_xZr₄(PO₄)₆ with any x for further investigation of controlled physical properties. The results indicated that Na_0.5Sr_0.75[ ]_0.75Zr₄(PO₄)₆ showed a near zero thermal expansion in the temperature range of 450–600 K, which can find potential applications.

中文翻译：

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NaZr ₂（PO ₄）₃ -SrZr ₄（PO ₄）₆固溶体的晶体结构，相变和热膨胀性能†

固溶体的晶体结构演变和与温度有关的相变对于理解功能特性的优化是非常需要的。在此，NASICON型NaZr ₂（PO ₄）₃ -SrZr ₄（PO ₄）₆固溶体的分子式为Na _{（2−2 x）} Sr _x [] _x Zr ₄（PO ₄）₆（0≤x≤1），其中[]表示空位，采用溶胶-凝胶法制备，并详细研究了它们的晶体结构，相变和热膨胀性能。在范围X = 0.3-0.35，有可逆的结构相变- [R Ç ↔ ř和的不同结构模型- [R相和- [R Ç相位被建立，以更好地理解相变机制。我们确定了R c和R结构之间的相变边界，并预测了Na _{（2−2 x）} Sr _x []的相变温度_{x x} Zr ₄（PO ₄） ₆和任何x用于进一步研究受控物理性质。结果表明，Na _0.5 Sr _0.75 [] _0.75 Zr ₄（PO ₄） ₆在450–600 K的温度范围内显示出几乎为零的热膨胀，这可以找到潜在的应用。