Encapsulated electroluminescent phosphor particles and method for making same. The phosphor particles are encapsulated in a very thin oxide layer to protect them from aging due to moisture intrusion. The particles are encapsulated via a vapor phase hydrolysis reaction of oxide precursor materials at a temperature of between about 25.degree. C. and about 170.degree. C., preferably between about 100.degree. C. and about 150.degree. C. The resultant encapsulated particles exhibit a surprising combination of high initial luminescent brightness and high resistance to humidity-accelerated brightness decay.