The hexagonal and monoclinic phase LaPO₄ and LaPO₄:Eu nanostructures have been controllably synthesized by a citrate-induced hydrothermal process at 100 °C. The crystal growth of LaPO₄ nanostructures was investigated, and the phase transformation of nanostructured LaPO₄ was systematically studied by varying the citrate concentration, pH value and reaction temperature. When 0.8 mmol of citrate was added into the reaction system, the hexagonal phase LaPO₄ transformed into the monoclinic phase. High concentrations of citrate would lead to the formation of hexagonal phase LaPO₄. The photoluminescence properties of the monoclinic phase LaPO₄:Eu prepared using a citrate-induced process demonstrate that the electric dipole transition (⁵D₀ → ⁷F₂) is stronger than the magnetic dipole transition (⁵D₀ → ⁷F₁), which indicated that Eu³⁺ is in a site with no inversion center. The strongest emission peak of hexagonal phase LaPO₄:Eu comes from ⁵D₀ → ⁷F₁. Furthermore, the citrate-induced hexagonal phase LaPO₄:Eu has a stronger emission intensity than the hexagonal phase LaPO₄:Eu prepared not using a citrate-induced process.

中文翻译：

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柠檬酸盐对 LaPO4 和 LaPO4:Eu 中相变和光致发光特性的影响†

六方和单斜晶相 LaPO ₄和 LaPO ₄ :Eu 纳米结构已通过柠檬酸盐诱导的 100 °C 水热过程可控合成。_{研究了LaPO 4}纳米结构的晶体生长，并通过改变柠檬酸盐浓度、pH值和反应温度系统地研究了纳米结构LaPO _{4的相变。}当向反应体系中加入0.8 mmol柠檬酸盐时，六方相LaPO ₄转变为单斜晶相。高浓度的柠檬酸盐会导致六方相LaPO ₄的形成。_{单斜晶相LaPO 4}的光致发光性质: 柠檬酸盐诱导制备的Eu表明电偶极跃迁（⁵ D ₀ → ⁷ F ₂）强于磁偶极跃迁（⁵ D ₀ → ⁷ F ₁），说明Eu ³⁺处于没有反转中心的站点。六方相LaPO ₄ :Eu的最强发射峰来自⁵ D ₀ → ⁷ F ₁。此外，柠檬酸盐诱导的六方相LaPO ₄ :Eu具有比六方相LaPO _{4更强的发射强度。}:Eu 未使用柠檬酸盐诱导工艺制备。