Spindly BaWO

4

crystals were synthesized by using a high molecular weight N-containing heterocyclic homopolymer

poly4-vinylpyridine（P4VP）

as a template.The well-defined shape of BaWO

4

crystals was characterized with scanning electron microscopy

transmission electron microscopy and X-ray diffraction.The size and shape of the spindly BaWO

4

crystals can be controlled through adjusting the pH value and the polymer concentration of the solution.The favorite spindly BaWO

4

crystals can be obtained at an appropriate polymer concentration.Spindly BaWO

4

crystals with various sizes were observed at low concentration of P4VP（

<

0.1 g/L）.When the concentration of P4VP was larger than 1 g/L

the dimensions of the spindles were more uniform and smaller.Very uniform BaWO

4

crystals with length of 2.5 μm were obtained at P4VP concentration of 10 g/L.The reactant concentration

i.e.the concentration of Ba

2+

and WO

2-

4

played an important role in the morphological control of the BaWO

4

crystals.At lower Ba

2+

concentrations（0.02 mmol/L）

only clusters without the spindly appearance were found.Spindly BaWO

4

crystals were obtained as the concentration of Ba

2+

was increased to 2 mmol/L.Further increasing Ba

2+

concentration to 20 mmol/L seriously distorted spindly BaWO

4

crystals formed.The pH value also affects the formation of BaWO

4

crystals.The increase of pH value promoted the formation of more uniform spindly crystals.Distorted BaWO

4

nanoparticles were obtained at lower pH values（

<

4）.Spindly crystals were obtained as the pH value increased to 6.5.More uniform small crystals were obtained when the pH value was increased to 8.The formation mechanism of the spindly BaWO

4

crystals was suggested according to the experimental results.We suggested that at appropriate conditions(such as pH range

concentration of Ba

2+

and P4VP)

the Ba

2+

should react with most suspended pyridyl to form BaWO

4

nanoparticles of various sizes at first

and then the residual pyridyl suspended on the main chain should react with the Ba

2+

in solution further to induce the orderly growth and aggregation of nanosized crystals

and spindly BaWO

4

crystals form at last.