The　heteroepitaxy　of　a　single　crystal　diamond　has　been　carried　out　in　the　KTaO3　substrate　using　Ir　as　a　buffer　layer.　KTaO3　has　a　perovskite　lattice　structure　and　displays　a　face-centered　cubic　structure.　Its　lattice　constant　is　3.98 Å,　which　is　only　3%　mismatched　with　the　lattice　constant　of　Ir　of　3.84 Å,　and　also,　its　thermal　expansion　coefficient　is　4.031 × 10−6/K,　which　is　nearly　close　to　that　of　diamond　3.85 × 10−6/K　(at　1223 K),　making　it　to　be　regarded　as　an　alternate　substrate　of　the　heteroepitaxy　of　a　single　crystal　diamond.　The　magnetron　sputtering　technique　was　used　to　deposit　Ir　thin　films　with　a　high　orientation　in　the　(001)　direction　on　a　KTaO3　(001)　substrate.　Thereafter,　bias　enhanced　nucleation　on　Ir　surface　was　grown　by　direct　current　chemical　vapor　deposition　(CVD)　methods.　At　last,　a　single　crystal　diamond　with　a　size　of　10 × 10 × 0.78 mm3　has　been　grown,　whose　(004)　rocking　curve　FWHM　is　183 arc　sec,　which　testifies　to　the　excellent　crystalline　quality　of　the　heteroepitaxial　diamond　film.　©　2021　Author(s).