In this paper many different shapes of ZnO crystals were synthesized by hydrothermal method when different mineralizer concentration and different temperature were used. When mineralizer concentration was less than 2mol/L KOH and the fill factor was approximately 35% at 350℃

only micro crystal ZnO was synthesized with size of several micron. When mineralizer concentration was more than 3mol/L KOH and the fill factor was approximately 35% at 350℃

many shapes of ZnO crystals were synthesized with many different size

the size of maximal crystal is from several decade micron to two hundred micron

the small size crystal is only several micron. When mineralizer concentration was respectively 4mol/L

5mol/L KOH

no bigger ZnO crystals were synthesized. The complete faces of ZnO crystal are exposed when high mineralizer concentration is used at 350℃

they are hexagonal faces

m

{10

1

0}

hexagonal cone faces

p

{01

1

1}

negative polar faces {000

1

} and sometimes positive faces {0001}. Sometimes many holes are observed on the faces of ZnO crystals

which shows bad completeness of crystal. When temperature was at 430℃ and mineralizer concentration was 2mol/L KOH

the bigger ZnO crystals were synthesized

the size of maximal crystal is several hundred micron

the small size crystal is only several micron. When mixture of 2mol/L KOH and 1mol/L KBr was used as mineralizer at 430℃

the size of maximal crystal is 1mm. When mineralizer concentration was 4mol/L KOH the size of crystals doesn’t get bigger. The exposed faces of bigger crystal synthesized at 430℃ are hexagonal faces

m

{10

1

0}

hexagonal cone faces

p

{10

1

1}

negative polar faces {000

1

}

the shapes of crystal are hexagonal cone

the faces of ZnO crystals are smooth

complete and the quality of crystals is higher than that of crystals synthesized at 350℃.