Chapter 1 Introduction 1.1 High-Pressure and High-Temperature (HPHT) Experimental Methods for Earth Science 1.2 MAA and HPHT Experimental Method 1.2.1 MAA 1.2.2 Types of MAA 1.3 M2SiO4 Group Members and Zn2SiO4 1.3.1 M2SiO4 Group Members 1.3.2 Zn2 SiO4 1.4 The Research Status of HP Zn2SiO4 1.5 Target,Content,Methods and Significance of This Research Chapter 2 Synthesis of HPHT Zn2SiO4 Polymorphs 2.1 Synthesis of Starting Materials 2.2 HPHT Experimental Synthesis for HP Polymorphs of Zn2SiO4 2.2.1 Preparation for Starting Materials for Zn2SiO4 Polymorphs Synthesis 2.2.2 Preparation for Anvils for HPHT Experiments Chapter 3 Experimental Methods 3.1 Electron Probe Microanalysis (EPMA) 3.1.1 Introduction 3.1.2 Selection of Standards 3.1.3 Conditions for EPMA 3.2 NMR Spectroscopy 3.2.1 Magic Angle Spinning (MAS) NMR Spectroscopy 3.2.2 29Si NMR Spectroscopy 3.2.3 Conditions for 29Si NMR Analyzing 3.3 Powder X-Ray Diffraction and Structural Analysis 3.3.1 Synchrotron X-Ray Diffraction 3.3.2 Conditions of Conventional X-Ray and Synchrotron X-Ray 3.4 Micro-Raman Scattering Spectroscopy 3.4.1 Interaction with Light.Raman Spectroscopy 3.4.2 Conditions for Micro-Raman Analyzing Chapter 4 Characterization of Zn2SiO4 Polymorphs 4.1 Chemical Compositions of Zn2SiO4 Polymorphs 4.2 29Si MAS NMR Spectra of Zn2SiO4 Polymorphs 4.3 Powder X-Ray Diffraction Patterns and Structural Analysis 4.4 Micro-Raman Spectroscopy of Zn2SiO4 Polymorphs Chapter 5 Solving Crystal Structure of Phase �� and Phase �� 5.1 Structure Determination by Powder Diffraction (SDPD) Method 5.2 A Useful Computer Program FOX for SDPD 5.3 Crystal Structure Refinement for Phase �� and Phase �� 5.3.1 Read Powder Diffraction Data from the Text File 5.3.2 Indexed by TREOR90 5.3.3 Space Group Estimation 5.3.4 Refinement of Crystal Structures of Phase �� and Phase �� by RIETAN-FP Program Chapter 6 Crystal Structures of Phase �� and Phase �� 6.1 The Results of Refinement from RIETAN-FP Program 6.2 The Obtained Crystal Structures of Two HP Zn2SiO4 Polymorphs 6.2.1 The Detailed Crystal Structure Information of Phase �� 6.2.2 The Detailed Crystal Structure Information of Phase �� Chapter 7 Discussion 7.1 Comparison of Zn2SiO4 and M2SiO4 7.2 The Phase Transformation of Zn2SiO4 Polymorphs (from Phase ��to Phase ��) 7.2.1 Phase �� 7.2.2 Phase �� 7.2.3 Phase \"Transformation\" from Phase �� to Phase �� 7.2.4 Comparison of ZnzSiO4 and ZneGeO4 7.3 Comparison of Zn2SiO4 and A2BX4 Type Inorganic Compounds Chapter 8 Conclusion References