Study On Electrical And Magnetic Properties Of Chinese High Pressure And High Temperature Grown Synthetic Diamonds

High pressure and high temperature grown synthetic diamond?HPHT synthetic diamond?is a semiconductor material and signal detection material with excellent physical properties,which has great application potential in the field of high-tech.However,the research on HPHT synthetic diamond in gemology is relatively limited.Almost none attention was paid to its electrical and magnetic properties.The data and information is missing.This paper investigates the electrical and magnetic properties of domestic HPHT synthetic diamond systematically and completely.The research results will add the relative contents and provide a new idea for the laboratory screening of HPHT synthetic diamond.In this study,HPHT synthetic grown diamonds with different colors grown by several representative Chinese producers were selected.The surface growth features and internal features of the HPHT synthetic diamonds were observed by means of a 3D microscope system,laser scanning confocal microscope,polarizing microscope and gemmological microscope.The distribution and content of impurity elements in the HPHT synthetic diamonds,the electrical parameters of the samples,as well as the relationship between electrical conductivity and impurity elements were investigated and analyzed by advanced analytical and characteristic techniques,such as X-ray fluorescence spectrometer,laser Raman photoluminescence spectrometer,Fourier transform micro-infrared spectrometer and Hall effect testing system.The magnetic parameters of HPHT synthetic diamond,natural diamond and CVD synthetic diamond were quantitatively measured using the magnetic measurement system of superconducting quantum interference devices?SQUID?,and the differences of magnetic properties were discussed.It was found that the conductivity of gem-grade diamond depends mainly on the distribution and concentration of boron.In colorless HPHT synthetic diamond,the content of boron was 0⁰.1 ppm.With the increasing of boron concentration,the conductivity increasing.Boron atoms are distributed mainly on?111?face in the diamond and concentrates on the surface.The distribution of boron leads to the uneven conductivity of HPHT synthetic diamond.The electrical resistivities of colorless HPHT synthetic diamond,natural diamond,and CVD synthetic diamond are2.7×10⁵?·cm,4.17×10¹²?·cm,1.9×10¹²?·cm,respectively.Colorless HPHT synthetic diamond is superior to the conductivity of the natural diamond and CVD synthetic diamond,electrical conductivity can be used as the basis for identification of screening HPHT synthetic diamond.The HPHT synthetic diamonds often contain the residual of metal catalysts,that leads to its ferromagnetism.HPHT synthetic diamonds with poor clarity can be attracted by hand-held magnets.The magnetic susceptibility of natural?HPHT?CVD synthetic diamond is 3.40³.80×10^-8.Natural diamonds and CVD diamonds display diamagnetism with no hysteresis.The magnetic characteristics of HPHT synthetic diamond are mainly affected by the internal magnetic inclusions.The purity level of HPHT synthetic diamond above VVS shows diamagnetism,while the purity level of HPHT synthetic diamond below VS shows ferromagnetism.As the purity level decreases,its saturation magnetization increases,which can reach 10^-1emu/g;coerced magnetic field increases,can reach 10²Oe;the remanent magnetization is also increased to 10^-2emu/g.HPHT syntietic diamonds with different clarity all exibit hysteresis.HPHT synthetic diamond can be effectively distinguished from natural diamond and CVD synthetic diamond according to whether there is hysteresis.