Synthesis Of SrTi_xZr_1-xO₃ Solution And Thermodynamic Analyze

In this paper the preparation of AB^â… _1-xB^â…¡_xO₃ based perovskites, SrTi_xZr(1-x)O₃ were studied,in which strontium nitrate,zirconium oxychloride,titanium tetrachloride and sodium hydroxide were employed as reactants.Firstly,the influence of experimental conditions to the phase of SrTi_0.5Zr_0.5O₃ were studied.Single factor method was used to find the optimal experimental conditions.Experimental conditions including temperature,the consistency of NaOH and stirring time were inspected. The result indicated that higher temperature,strong alkalis condition and longer stirring time were propitious to compound SrTi_0.5Zr_0.5O₃.It showed that the optimal experimental conditions was that 80℃,[NaOH]= 3mol/L,and stirring 2h.The structural phase of SrTi_0.5Zr_0.5O₃ was cubic perovskites phase though XRD analyzing.In another words crystal formation rate is as control procedures.According to the experimental condition preparing SrTi_xZr_1-xO₃, direct precipitation-aging process was applied to synthesize SrTi_xZr_1-xO₃ solid solution which also is cubic perovskites phase.Direct precipitation process was applied to synthesize SrTi_xZr_1-xO₃(x＞0.4) solid solution at the condition which is the optimal experimental conditions to prepare SrTi_0.5Zr_0.5O₃.In addition crystalline SrTi_xZr_1-xO₃(x＜0.4) can be obtained only when the corresponding composition precipitates were aged for a period of time.It is discovered that aged time is the principal factor to the prepare SrTi_xZr_1-xO₃.It is because that the radius of Zr⁴⁺ is larger it comes into lattice becomes more difficult to form stable solid solution when the consistency of Zr is increasing.In order to reveal the experimental phenomena the simple addition model and the Bragg-Williams model were used to calculate the free energy of SrTi_xZr_1-xO₃.Then according to the Gibbs function criterion principle thermodynamics,the Gibbs free energy of SrTi_xZr_1-xO₃ were calculated by a designed route.So the reason that SrTi_xZr_1-xO₃(x＜0.4) can be obtained though extending aging time when the consistency of Zr is increasing.The Gibbs free energy of SrTi_xZr_1-xO₃ is increasing with the consistency of Zr increasing,in other words the driving force is decreasing.When x is less than 0.4 SrTi_xZr_1-xO₃ can not be obtained by direct precipitation because the Gibbs free energy of SrTi_xZr_1-xO₃ is smaller.