dor123
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| Is there any advantage for the lithium impurity in white QMH lamps?
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James
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| Yes and no. It improves the CRI quite dramatically, but also reduces life. Lithium iodide is far more corrosive towards quartz than sodium iodide, due to its smaller atoms which more easily penetrate and attack the silica structure.
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dor123
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| Just a shame. However, the lithium that originates from the quartz isn't LiI. No?
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James
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| Yes lithium is almost always present as an impurity in quartz, but often even more is added in the halide dose.
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Ash
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| How does the Quartz withstand the Lithium ? I would expect it to be quite unhappy, considering that the most similar other elements are Sodium and Cesium ?
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dor123
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Yes lithium is almost always present as an impurity in quartz, but often even more is added in the halide dose.
But is this lithium impurity have an advantage in white MH lamps, like increasing the CRI? |
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I"m don't speak English well, and rely on online translating to write in this site.
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I lives in Israel, which is a 220-240V, 50hz country.
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RRK
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How does the Quartz withstand the Lithium ? I would expect it to be quite unhappy, considering that the most similar other elements are Sodium and Cesium ?
Elementary lithium from Li additive does not touch the glass much, it recombines with halogen outside the arc, forming relatively inert halide salt. Natural lithium may present in quartz, but as some millionth fraction, not affecting the properties. |
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RRK
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But is this lithium impurity have an advantage in white MH lamps, like increasing the CRI?
Natural impurity practically too weak to affect light-technical properties of the lamp significantly. Deliberate addition of Li salt sure does, and is widely practiced. Osram's American style 3000K low-power HQI-E multiband NaSc lamps is one example, also widely used in pink colored MH lamps, with or without sodium. HQI-E 3K lamps look having pretty decent life despite obvious lithium addition, BTW. |
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« Last Edit: Today at 02:08:34 AM by RRK »
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dor123
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@RRK: R U sure that the Osram HQI-E 70-150W/W USA have LiI? My Sylvania HSI-TD 70W/WDL and my Aliexpress 70W 3000K MH lamps have both Na-Sc without Li.
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James
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| Actually the natural lithium impurity in the quartz has a very profound impact on the spectrum, and life.
It is very difficult to make lithium-free quartz, and it leaches out only slowly. Actually most new lamps do not show Li spectra lines, but after some hundreds and thousands of hours burning its spectral lines become progressively stronger, and cause some CRI increase.
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RRK
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@RRK: R U sure that the Osram HQI-E 70-150W/W USA have LiI? My Sylvania HSI-TD 70W/WDL and my Aliexpress 70W 3000K MH lamps have both Na-Sc without Li.
I am 101% sure, as I have seen the spectrum may times with multiple instruments. Your double-ended RX7s lamps have absolutely nothing to do with this old-school protected American-originated lamp. Here is a hi-res spectrum catched from my HQI-E 70W/WDL Sure there are some huge orange and deep red peaks from Li additive. Somehow Sylvania still managed to get a decent life from these despite a large lithium amount... Btw Osram seems a bit ashamed and tends to be a bit shy  about this lamp CRI and never publishes the exact number. No wonder why, my HP320 thinks it is just a mediocre 70-73. |
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Ash
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| The spectrum looks like it would be nice and pleasant light. If anything, the CRI number may indeed not do it justice
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