as mentioned above , under certain conditions , electron transfer between a pair of rare earth ions which are electronic configurations conjugate can be achieved , and abnormal valence changes thereof can occur . for example , eu 3 + and tb 3 + are such a pair of conjugate rare earth ions which , in certain substrate , have the following equilibrium : eu 3 + + tb 3 + = eu 2 + + tb 4 + . therefore , in a given substrate , three ions , which are eu 3 + giving red light , tb 3 + giving green light and eu 2 + giving blue light respectively , can coexist and form a trichromatic phosphor , while tb 4 + is not luminescent . further , ce 3 + and eu 3 + are also a pair of conjugate rare earth ions and the following equilibrium can also exist between them in certain substrate : eu 3 + + ce 3 + = eu 2 + + ce 4 + . therefore , in the above trichromatic phosphor , if ce 3 + is further added , then it can not only sensitize tb 3 + , but also regulate the concentration of eu 3 + and eu 2 + . according to the present invention , the following three systems doped with rare earth ions europium ( eu 3 + ) and terbium ( tb 3 + ) can be used to prepare the trichromatic phosphor : ( 1 ) calcium boron phosphate which can be expressed by a chemical formula of cabpo 5 : xeu : ytb , and a system which further comprises cerium ion ( ce 3 + ) as a sensitizing agent and can be expressed by cabpo 5 : xeu : ytb : zce ; ( 2 ) calcium boron aluminum phosphate which can be expressed by a chemical formula of caal r b 1 - r po 5 : xeu : ytb , and a system which further comprises cerium ion ( ce 3 + ) as a sensitizing agent and can be expressed by caal r b 1 - r po 5 : xeu : ytb : zce , wherein r is a mole fraction with r = 0 . 5 – 0 . 8 ; and ( 3 ) calcium chloride oxygen boronat which can be expressed by a chemical formula of ca 2 b 5 o 9 cl : xeu : ytb , and a system which further comprises cerium ion ( ce 3 + ) as sensitizing system and can be expressed by ca 2 b 5 o 9 cl : xeu : tb : zce ; in all of the above formulas , x , y , z all mean mole fractions , and x = 0 . 02 – 0 . 05 , y = 0 . 001 – 0 . 01 , z = 0 . 001 – 0 . 01 respectively . after having been grounded and mixed , the materials are reacted for 3 – 5 hours both in air and at 800 – 1000 ° c . the resulting products were cooled and then a white powder is obtained . finally , the products in the form of white powder were excitated using ultraviolet light of a wavelength of 365 nm or 254 nm to obtain a trichromatic phosphor in which three wavelengths of 611 or 614 nm , 544 or 545 nm , 402 or 430 nm respectively can coexist . according to the present invention , only one , but not three , kind of matrix compound is needed to produce the present rare earth trichromatic phosphor ; and only two , but not three , kinds of rare earth reactive ions are doped : eu 3 + and tb 3 + . moreover , the eu 2 + giving blue light is obtained through the electron transfer between eu 3 + and tb 3 + , in which , no reducing agent is needed . in addition , it can be synthesized in air . thus this process is simple , and will not cause any environmental pollution . if ce 3 + is used , a better sensitization effect can be obtained . eu 2 o 3 , tb 4 o 7 , both with purity of 99 . 99 %, caco 3 , b 2 o 3 , ( nh 4 ) 2 hpo 4 , all with analytical purity , were weighed in a stoichiometric way . eu 3 + was added with a mole fraction of 0 . 05 , tb 3 + with a mole fraction of 0 . 01 . ( nh 4 ) 2 hpo 4 is in excess of 10 %. they were grounded and mixed in agate mortar and put in a si — c tube furnace , heated at 300 ° c . for 20 minutes and then heated at 850 ° c . for 5 hours , cooled to room temperature . the product is a white powder . its crystalline structure was determined by x - ray diffraction analysis . the powder was excited at 365 nm and 254 nm respectively , the emission peaks for eu 3 + , tb 3 + , and eu 2 + are at 611 nm , 544 nm and 402 nm respectively . the emission intensity at 365 nm is stronger than that at 254 nm . ceo 2 , eu 2 o 3 , tb 4 o 7 , all with purity of 99 . 99 %, caco 3 , b 2 o 3 , ( nh 4 ) 2 hpo 4 , all with analytical purity , were weighed in a stoichiometric way . eu 3 + was added with a mole fraction of 0 . 05 , tb 3 + with a mole fraction of 0 . 01 , ce 3 + with a mole fraction of 0 . 01 . ( nh 4 ) 2 hpo 4 is in excess of 10 %. they were grounded and mixed in agate mortar and put in a si — c tube furnace , heated at 300 ° c . for 30 minutes and then heated at 900 ° c . for 4 hours , cooled to room temperature . the product is a white powder . its crystalline structure was determined by x - ray diffraction analysis . the powder was excited at 365 nm and 254 nm respectively , the emission peaks for eu 3 + , tb 3 + , and eu 2 + are at 611 nm , 544 nm and 402 nm respectively . in comparison , example 1 , the emission intensities of tb 3 + and eu 2 + are stronger . the synthesis of caal 0 . 8 b 0 . 2 po 5 : xeu : ytb system eu 2 o 3 , tb 4 o 7 , all with purity of 99 . 99 %, caco 3 , al 2 o 3 , b 2 o 3 , ( nh 4 ) 2 hpo 4 , all with analytical purity , were weighed in a stoichiometric way . e 3 + was added with a mole fraction of 0 . 02 , tb 3 + with a mole fraction of 0 . 005 . ( nh 4 ) 2 hpo 4 is in excess of 10 %. they were grounded and mixed in agate mortar and put in a si — c tube furnace , heated at 360 ° c . for 20 minutes and then heated at 950 ° c . for 5 hours , cooled to room temperature . the product is a white powder . its crystalline structure was determined by x - ray diffraction analysis . the powder was excited at 365 nm and 254 nm , the emission peaks for eu 3 + , tb 3 + , and eu 2 + are at 611 nm , 544 nm and 430 nm respectively . the emission intensity at 365 nm is stronger . the synthesis of caal 0 . 8 b 0 . 2 po 5 : xeu : ytb : zce system ceo 2 , eu 2 o 3 , tb 4 o 7 , all with purity of 99 . 99 %, caco 3 , al 2 o 3 , b 2 o 3 , ( nh 4 ) 2 hpo 4 , all with analytical purity , were weighed in a stoichiometric way . eu 3 + was added with a mole fraction of 0 . 02 , tb 3 + with a mole fraction of 0 . 005 , ce 3 + with a mole fraction of 0 . 001 . ( nh 4 ) 2 hpo 4 is in excess of 10 %. they were grounded and mixed in agate mortar and put in a si — c tube furnace , heated at 360 ° c . for 20 minutes and then heated at 950 ° c . for 5 hours , cooled to room temperature . the product is a white powder . its crystalline structure was determined by x - ray diffraction analysis . the powder was excited at 365 nm and 254 nm , the emission peaks for eu 3 + , tb 3 + , and eu 2 + are at 611 nm , 544 nm and 430 nm respectively . compared to example 3 , the emission intensities of tb 3 + and eu 2 + are stronger . the synthesis of ca 2 b 5 o 9 cl : xeu : ytb system eu 2 o 3 , tb 4 o 7 , all with purity of 99 . 99 %, caco 3 , h 3 bo 3 , cacl 2 . 2h 2 o , all with analytical purity , were weighed in a stoichiometric way . eu 3 + was added with a mole fraction of 0 . 04 , tb 3 + with a mole fraction of 0 . 01 . they were grounded and mixed in agate mortar and put in a si — c tube furnace , heated at 300 ° c . for 20 minutes and then heated at 850 ° c . for 3 hours , cooled to room temperature . the product is a white powder . its crystalline structure was determined by x - ray diffraction analysis . the powder was excited 365 nm and 254 nm , the emission peaks for eu 3 + , tb 3 + , and eu 2 − are at 614 nm , 545 nm and 430 nm respectively . the emission intensity at 365 nm is stronger . the synthesis of ca 2 b 5 o 9 cl : xeu : ytl : zce system ceo 2 , eu 2 o 3 , tb 4 o 7 , all with purity of 99 . 99 %, caco 3 , h 3 bo 3 , cacl 2 . 2h 2 o , all with analytical purity , were weighed in a stoichiometric way . eu 3 + was added with a mole fraction of 0 . 04 , tb 3 + with a mole fraction of 0 . 01 , ce 3 + with a mole fraction of 0 . 005 . they were mixed in agate mortar and put in a si — c tube furnace , heated at 300 ° c . for 20 minutes and then heated at 850 ° c . for 3 hours , cooled to room temperature . the product is a white powder . its crystalline structure was determined by x - ray diffraction analysis . the powder was excited at 365 nm and 254 nm , the emission peaks for eu 3 + , tb 3 + , and eu 2 + are at 614 nm , 545 nm and 430 nm respectively . compared to example 5 , the emission intensities of tb 3 + and eu 2 + are stronger .